[Multiplayer] All hostile mobs in dimension despawn when player enters dimension

I cannot reproduce this in singleplayer. (Did not try multiplayer with spectators, which may somehow interact.)

I have tested some more now. In some random single player worlds it works fine. In most of my single player tests I have this bug. I haven't checked on any other snapshot servers. The map from the server worked fine when I opened it in single player. It's really weird. I don't know what triggers this bug nor do I know why it happens so"randomly", maybe there is a pattern I haven't noticed yet.

Edit: I now think it's multiplayer only

I have added a video that showcases the bug in the latest snapshot (16w07b)
You can find it here; https://www.youtube.com/watch?v=dXv8AXMKe7Y

for hostile mobs without the PresistanceRequired tag sat to 1, a player must be online and loading them, or they'll despawn

The thing is that the mobs don't despawn when I leave the area. They despawn when I enter the dimension. Normally XP farms like this design work fine. (I recommend you to watch my video, then watch any other video of a XP farm that sends mobs to an other dimension because of the local mob cap)

I was having the same issue and today, after entering the nether for the second time, some mobs appeared.
After going back to the overworld for some time and back to the nether, the farm seems to be working again. I'm not quite sure what happens, I'll try to reproduce what's going on.

Same issue - running server. I also have a guardian XP farm that uses the nether to bypass the mob cap. Mobs despawn when changing dimensions.

I also encountered this bug on my guardian xp farm. I stayed in the nether in spectator mode whilst someone sent guardians through the portal in the overworld. I could see them going through, all good. But the instant he entered the nether through the nearby portal they despawned. Also all other mobs in the nether despawned and new ones spawned around him at that instant.

Same here. I built a guardian farm single player (though for a while, I did have the save file on a server - It's now back on single player only) which involves sending the guardians to the nether to get around the local mob cap... I've been having this issue since the 1.9 update. Sometimes when I AFK in the overworld near the farm & then return to the nether, the guardians are there. Other times, they all despawn in the holding tank leaving only 2-3 who are still falling through the portal.

It's been exactly one year now since I opened this ticket and still nothing happened... The ticket hasn't even been confirmed.. Shouldn't there be some progress by now?

I'm currently having this issue right now!!! (playing on PC version on a Realms server/Java/1.11.2) Help! I've just finished building a guardian xp farm that sends the mobs to a portal and crusher in the nether. Very disappointing that i have no mobs every time I come into the nether. My entrance portal is less than 32 blocks from the mob entrance portal. Zero mobs every time I come in. Something is essentially different about the way the dimensions are loaded on servers compared to single player... Has it been this way in the past? This is the first time I've tried sending mobs through a portal. I had plans for using some ghasts in the overworld but this bug will ruin that as well 😞

Really pisses me off, spent 3 weeks on my guardian farm just to find that is doesn't work because of a stupid bug

I'm also playing on my own 1.11.2 multiplayer server and the problem still persists. Likewise I have a guardian farm that sends guardians to the nether, which I spent many days building all in Survival. It doesn't work at all now. There are numerous reports of this same bug throughout bugs.mojang.com. Many of them claimed to be resolved. Yet no resolution is actually given on any of the many bug reports and their duplicates.

The best Mojang mods have offered is simply to reiterate that mobs despawn if the chunk is unloaded, completely ignoring, time after time, the specific situation people are explaining. That is, bobs being sent to a completely unloaded chunk in the nether, where mobs should remain in an unloaded state until a player enters the nether, at which point they should be there.

Nether portals have worked this way since they were introduced in Beta. They continued to work this way up until some point in release 1.8. Yet the the mods here reply as if this change never happened, neither confirming it was an intentional change nor admitting it is a bug.

The simple fact is that the way mobs despawn in other dimensions changed radically and broke the functionality of many complex, time consuming builds. It has been over a year and the developers still won't even say if it's a bug or an intentional change (which is unlikely since it only changed for multi-player but not single-player), let alone actually try to resolve the issue.

Is this still a issue in the latest version of the game(currently 1.13.1)?

If so, please add it to the affected versions, thanks!