I just upgraded from the previous version to the r2.1-242 version on my server. When restarting my server it crashes out with :

Quark (quark) has failed to load correctly
§7Attempted to load class vazkii/quark/base/client/BLMHandler for invalid dist DEDICATED_SERVER]

Never had issues with Quark before, love this mod. Doing a quick search I found similar issues in other mods that had been solved suggesting I didn't just do something stupid on my side (not that I've ruled that out yet :P ). Since its only 3 hours since the update was submitted I thought I should make sure to bring it to your attention.

Here is the latest.log : https://pastebin.com/uGC2d5KP

MineCraft 1.15.2
Forge 1.15.2-forge-31.2.0
AutoRegLib-1.5-40
---------------------------->

BLMHandler is the black screen that appears when you launch the game with the update for the first time (or every time if you use 243). This should be fixed now.