Latest version works beautifully in single player worlds, but crashes my small family server on startup. The first thing that springs to mind is Forge? Should this release be compatible with Forge 14.23.4.2705, or should I update?

crash-2018-11-29_18.00.55-server.txt

https://github.com/Vazkii/Quark/blob/16b8f4553f2317febcf60afc48a152976cf1ef98/src/main/java/vazkii/quark/oddities/feature/Backpacks.java#L48
Welp, someone didn't test the mod on a server...

Heh seems like it.

Ditto, got about the same crash log here.