This happens on servers as well, I'll be on a vanilla server or world and I'd get pushed back, and as a result lose progress or die. It's happened if the world is over 100 MB in size, which is terrible because I've considered starting making my world a forever world and it started happening 1.21.71.
Affects Mobile, PC and Xbox as well. Realms, BDS and Single player worlds are also hit with this since 1.21.70 and 1.21.71 hotfix
We've found that it was mostly Furniture mods, but there are some other mods that have this issue too. PC has been crashing but Console and Mobile can join just fine.
It occurs on BDS mainly, I haven't had any issues joining the public servers that are in the home page. Just any custom servers on bedrock.
This was fixed in 1.21.71, however, it was affecting BDS, Realms, and single player at the time. It was fixed in 1.21.71.