Margaret Boesch

All I know is I can't play it this way, because soon as I enter a mangrove swamp and this starts happening, my stuff gets laggy AF, like I'm counting seconds to the frame, not frames a second!  Makes the game no. fun. at. all.

I have seen this exact same wierdness.  Also in pools below Y-0 the top layer of lava does not render at all.  I have nearly died a few times in invisible lava.  Now I've gotten into the habit of throwing some cobblestone into areas that look otherwise clear to make sure they don't burn up before I step down.

Tim Roush is your golem dressed like a shoe salesman?  I think I'm having flashbacks of Mulligan from Cabin Boy..

I noticed this well before the nether update, and it still persists.  The world-generated village I'm currently trading in began overpopulating with no rhyme or reason, and I hadn't altered anything.  I've added beds and placed work stations because I felt bad for all the poor unemployed villagers roaming around at night, and they've rewarded my responsible stewardship by continuing right on making more babies! There are little ankle biter villager rugrats everywhere!  And I just know they're going to grow up to be homeless, no-bed-having, night-roaming burdens on society!
Maybe we need a splash potion of contraception as a new item in the next update?

Any similarities in the file sizes when your worlds start crashing, Joe?  I've found on my most recent world, the save file size is frozen at 1019MB and won't increase no matter what I do.  There's no warning that I'm running out of space, and there's still plenty of room on my HD anyway.  The file size just stops changing and the world starts crashing.  I've started a new seed to see if I it crashes again when I reach 1019MB.

What Ian said!  It's far simpler to upvote than comment.  So if you have to pick one, vote on this issue so Mojang will address it!
Joe, did you find a trend with all the worlds you restarted?  Any common denominators?  Can you upload them so the Mojang gurus can examine them?

So, fellow concerned players, I've been thinking some more about this, for those of us who have awesome worlds at stake and don't want to lose them permanently.  Of course, there's no guarantee that fixing the bug will fix our worlds.  But I'm pretty sure the more corrupted they get, the less likely they are to be successfully salvaged.  I'm also pretty sure the more we continue playing them, the more corrupted they are getting.  Bearing those two circumstances in mind, perhaps, for now, the best thing to do is for us to quit playing those worlds until this bug is fixed.  Take the intervening time to check out some new seeds; you might find one even better than the one you got.  Or use your current seed to create a fresh world, if there are things you would have liked to have done differently.  We have two directions we can go after that:  We can decide to not get too committed to our new worlds and move on to a new seed once the file size reaches 1019MB.  Or, we could possibly use this opportunity to create a useful tool for helping our Mojang techs.  Play with multiple players, play on local networks, play across different platforms with your new worlds; see if you can reproduce the bug and make them crash.  If we can discover some common denominators with this bug, it might actually help it to get fixed faster.  But we should probably leave our current worlds alone if we want to maximize the chances of being able to save them.
Just some thoughts, for what it's worth.  If nothing else, it's something to do.  Because time drags when you're nonessential and under stay-at-home orders...  🙂

I can't help noticing that now that my world keeps crashing, the hotfix news screen listing all the fixed bugs(that I oddly didn't have) shows every time at startup.  I used to only see hotfix notifications once.
You know what would be nice?  I'd like to be able to revert to the version that didn't cause problems for me.  As a PS4 user, updates download and install whether I want them or not.  I'd really like to be able to have the choice of installing them, or at least be able to uninstall them if they cause me more problems than they solve.

^^  Inconvenient as all-get-out, but true.  😞  But hey, as long as I can get a world at some point in the future that won't do this stuff, I could live with starting over one more time.  My current seed is kind of crappy anyway.  All the cool stuff like jungles, badlands and woodland mansions are SO far away that I have to teleport to them or literally spend all day trekking.  My last seed was way cooler.  It was littered with woodland mansions, and every kind of biome was reasonably close.  I even stumbled across two fossils and a stronghold within 3000 blocks of where I spawned!  I was really, really ill when that world corrupted.

Right there with you, Jesus.  I'm having this problem on PS4 as well, and also losing entire worlds.  But the game is buggy in general.  It seems the updates often lead to other problems, and they drop a lot of updates on us.  It doesn't help, either, that the bugs take a long time to fix.  I mean, there's a lot of them, and they have to fix them all.  We're in a queue here.  There are other bugs in line ahead of the one we're experiencing.  But make no mistake; if there's a shafting going on, it's not a discriminatory shafting.  The Bedrock codebase is on multiple platforms.  This means the good news is, when they fix this bug on Switch and Xbox One, it'll probably be fixed on PS4, too.  Again, we all share the same codebase.

Ah, yes.  The dreaded "Pink Checkerboard Screen of Doom."  I've been enduring this for weeks now.  I'm on PS4 and it seems to happen whenever my world exceeds 2GB in size.  It gets even worse when another player joins the world and travels more than 1500 blocks away from my player.  Even after the player stops joining, the world just crashes more and more.  I've tried deleting and reinstalling my world from online storage.  I've gone into saved game data and deleted corrupted data(when I can find it, sometimes it doesn't show up.)  I've even gone into PS4 safe mode and rebuilt my database.  Nothing seems to help.  And eventually, if this time goes like the last time when I ended up having to delete a world and start over, it will probably crash more and more until I just can't open the world at all.  I'm honestly about to quit this game for good.  Losing all that work and time invested is seriously playing with my emotions....

UPDATE:  The last world I lost made it up to 2GB before it corrupted.  However, I looked at the world I'm currently having issues with, and it seems frozen at 1019.0MB.  My backup copy registers the same size, and I've added a considerable amount of data since then, I'm sure.  I'm noticing that's a recurring theme in the comments.  Again, it makes no difference now if players join or if I'm playing alone.  It also makes no difference if I'm online or offline.  I may be able to play for hours before the crash, and sometimes the game crashes seconds after I open my world.  I've started playing my world in creative mode instead of survival.  It doesn't seem to be crashing in creative mode, so far.  I'll update if this changes.
Meanwhile, I'll try to get my world data forwarded to the experts.  PS4 won't support less than a USB 3.0 drive, and I don't have one.  It's gonna take a few days to order one.  I'm not going to the store for it, because, you know, Wuhan Plague.

UPDATE 2:  Nope.  It crashed in creative mode, too.  Just now.  It immediately got the Pink Checkerboard Screen of Doom as soon as the world opened.  Then I tried to open it again and got the Dirt Screen of Doom with the message, "There was a problem loading this world."  Oh dear, that's exactly what happened with the last world.  Eventually my world would never advance further than that screen and I wasn't able to open it at all.  I'm gonna lose this world.  Shucky darn.

The same exact thing happened to me just yesterday on the PS4 console.  I just finally started playing with someone else on Nintendo Switch. (I'd really love to know how soon is soon when you say featured lobbies are coming soon, because it's really hard to find friends to play with when you can't go on a lobby and make friends.  I just got PlayStation Plus for the first time so I could play with others online, and I've been paying for access for the past three months for basically nothing, other than waiting for featured lobbies to actually "come soon."  But that's another matter.)  Anyway, less than five minutes after my friend joins the game, boom, "Disconnected due to corruption."  All my friend had time to do was punch a tree, and we both got kicked.   On the world select screen, the preview looked like I had lost at least an hour of progress.  Then the world wouldn't load.  "There was a problem loading this world," it would say.  Luckily, I backed out of the game and restarted my PS4, and my world did load.  I had lost about 10 seconds of my game, thankfully.  But if this continues every time a friend comes on, I'm discontinuing my PlayStation Plus access and giving up on the featured lobbies that are allegedly "coming soon."  What's the use of paying hard earned money every month for nothing??