The datapack directory under YourDataPack/data/YourDataPack gets deleted when uploaded to Realms. I tested this, uploading a world that had a datapack installed, then downloaded it again and found only the /minecraft/ folder in the datapack folder. Everything else (all functions) were removed.
I also have this issue. I downloaded the world after uploading it, and in the datapacks/data folder, I see only the minecraft folder. The one for my datapack functions is missing.
As a point to anyone working on datapacks, the entire directory to an mcfunction file is treated as a string, that can't be longer than 100 bytes. Keep that in mind if you like to have heavily sorted files like I do.
There was no crash.
Ah. Uh, sorry. I was just corrected on MCForum as well. That value is inputted as a string. Hadn't looked at it that way.
Confirming I have this issue.
As of 1/7/2018, I get this quite frequently still. Today there have been 4 of us all on at various times, and we each get kicked occasionally all at the same time.
@Chris, you're welcome man. I had a day off and spent it crying because I couldn't play this game. Then I noticed I couldn't read, and then I cried some more. Now I can play, so I'm not crying. Yeah man.
See tickets 622-627.
Dustin Cox, no. The more people that find the existing bug ticket, make a comment reporting as much information as they can IN ONE PLACE, and then maybe upvote the bug ticket, the better.
*edited to clarify
Duplicate of 624, 623 and 622.
We duplicated this issue here because we suck and can't read.
Can confirm, have this issue on my Realms server today. While mining I first noticed I was unable to pick up blocks. I assumed some network issue had reset my session or some such, so I restarted Minecraft. But I got the netty error while attempting to log in. My daughter also tried logging in, and she has the issue as well. I tried switching active worlds and got an error that simply read "504".
**update - came back online but reverted to a 30 minute old save, losing half an hour of mining.
This also happens to me. When I first start up the game it runs fine. If I leave a world and enter a world (whether the one I had just left or a new one) this bug happens. I have to exit Minecraft and then load the game back up from the launcher to clear the bug.
Also, it continues playing the music from the game's home screen over top of the music the game world plays.
Can't add attachments, but here's a screenshot. http://i.imgur.com/UgDlE1w.png
I have this issue as of 1.19.41. This is a seriously old bug.
Desktop, tablet mode disabled (of course), AMD drivers, everything up to date.