i got some weird issues with optifabric: when placing blocks every 3rd or 4th block ghosts for a split second which causes me to fall through that block sometimes. i tested some stuff: took out optifabric from my modfolder and used vanilla with regular optifine, no issues in both of those cases. also i use both most recent updates of optifine and optifabric. general performance apart from that issue is good. is there any way to fix this?

Are you using Lithium too? This is a sign of lag in the internal server

I also have this problem.
Optifine without fabric + optifabric has no such error