So i created a shell can changed to it, but once i did this my game removed me from the server. oce i tried to rejoin it gave me the message:
"Internal exception: io.netty.handler.codec.DecoderException:
java.io.IOException: Packet was larger than i expected, found 446325
bytes extra whilst reading packet 53"

now my friend went towards my shell storage and construct and the same thing happens to him?

Most likely not the fault of sync. The only thing I can imagine with sync involved is some player NBT getting really huge. And then there is not much we can do. Need the complete stacktrace (log) to see that though.

I just had the same issue;
This occurred upon trying to switch to a newly created shell after entering a shell storage:

I was just wondering if there's a way to fix this, including by removing mods or using MCEdit to remove some blocks that may be crashing
Edit: Removing Sync fixed it

This error, followed by a "Packet was larger than I expected" error is at the end of the log:
latest.log

Note: I was able to continue playing after having someone teleport me out of my base, but the error repeats when I return