In my serverlog it says "[chiselsandbits]: Unable to determine blocks eligibility for chiseling" for some of the blocks in the mod.
I read up on the error (ChiselsAndBits/Chisels-and-Bits#49) and it seems it can't be fixed by @AlgorithmX2.
These are the blocks:
vazkii.quark.automation.block.BlockObsidianPressurePlate attempted to load net/minecraft/client/renderer/ItemMeshDefinition
vazkii.arl.block.BlockModStairs attempted to load net/minecraft/client/renderer/ItemMeshDefinition
vazkii.arl.block.BlockModSlab attempted to load net/minecraft/client/renderer/ItemMeshDefinition
vazkii.quark.base.block.BlockQuarkTrapdoor attempted to load net/minecraft/client/renderer/ItemMeshDefinition
vazkii.quark.decoration.block.BlockColoredFlowerPot attempted to load net/minecraft/client/renderer/color/IItemColor

@AlgorithmX2 what would I do to fix this?

You have one or more methods on your Blocks ( BlockColoredFlowerPot, BlockModSlab, BlockModStairs, BlockObsidianPressurePlate, BlockQuarkTrapdoor ) that refer to Client side classes, ItemMeshDefinition, and IItemColor and such in particular based on the error.

Adding a @SideOnly(Side.CLIENT) to such methods will resolve the issue and allow java to load the full classes without throwing an error.