A client unexpectedly crashed, it seems the logs were pointing out to polymer and another mod called Connectivity

Logs: https://mclo.gs/ZnmlhFB

Thanks you, I'll report it to the create devs..

I also reported it here someaddons/connectivity#80

This error is not caused by polymer (or connectivity in that matter).
The crash points to Create mod (so it can be create, it's addon or some other mod that changes rendering).

The Invalid BlockState ID errors are caused by the crash, which puts game into invalid state (makes both disconnect logic and packet reading logic run at the same time, which creates garbage data)