It sounds like, but it isn't. Because why should the server receive the message INSTANTLY, but the client not?
Also the ping to the server says 80ms. Which isn't bad considering the client is in germany and the server in the us.
"Some entities are moving, some are stuck staying in one place." <-- This is also a proof that a bad connection is not the case. If I had a bad connection all entities would be stuck. Not just a few.
It has to be some kind of problem with the MC Server. Because If I "do stuff" like breaking blocks, die etc. and then disconnect, the console spams Netty packet errors.
<-- This. So the server is queuing all packets up, and when I disconnect it cancels the packets.
EDIT:
Also I was stupid. I've removed all mods and started the wrong server before. With no mods. I have no problem whatsoever. So not a forge problem. Guess that means disabling mods until it doesn't happen anymore.
EDIT2:
It doesn't happen with other big modpacks, such as Direwolf20, FTB Infinity.