After updating to 2.8.0 from 2.7.2 I started to get stuck in when I entered the world(I was in a LAN with a friend, it happened to him too). After checking every mod I updated and using Kiwi alone (both 2.8.0 and 2.8.1), I noticed this seems to happen the second time you enter a world/after entering a second world. If you teleport in the air you remain in the position you teleported, the item in your hand(and your hand) appear lower than where they should be, you mine at a slower speed and items and blocks you pick up are bugged. You can still move your camera though. The only way I found to get out of this state is to get killed(you still take damage and commands can kill you). The versions of Forge I used(I tested on both) are 31.2.31 and 31.2.0. Sorry for the long post but I tried to give you as much details

Please provide your debug.log. It is in logs folder

Here you go! I put the latest log too, it may be useful
debug.log
latest.log

Thank you! the fix won't be too late