We've been seeing a lot of the message below on the official Enigmatica 6 server:

[27Dec2020 02:36:20.414] [Server thread/INFO] [chiselsandbits/]: Unable to determine blocks eligibility for chiseling, wayoftime.bloodmagic.common.block.BlockBloodRune attempted to load net/minecraft/client/util/ITooltipFlag missing @OnlyIn( Dist.CLIENT ) or @Optional?

It happens for all sorts of blocks.

For any bug reports please provide the following details as well,

• MC Version: 1.16.4
• C&B Version: 0.2.8-RELEASE
• Do You have Optifine: No

Damn, I was hoping it was on your side, because it's several mods and about a hundred blocks :P Oh well. Thanks!

@NillerMedDild This might be an issue with BloodMagic not marking its methods properly with @onlyin (Dist.Client)

Nothign I can do.
Please report it to them.

Well the error is not really a problem.
It is just a warning.
You can t chemically just ignore it.