If the [1] Armor Curve Toggle option in the config is false (the default value), then the game will crash when an entity attacks another entity.

The full backtrace: https://gist.github.com/Fuyukai/519495a6f516e3403c1ba7b8bb1fbcfa

The root cause is that it attempts to access UTArmorCurve.armor#with unconditionally in the UTDamageCalculatorMixin mixin, but UTArmorCurve.armor doesn't get set to a value unless that option is set to true.

It also prevents you from attacking any entity with the same error (but the game traps it in the networking code so it doesn't crash).

Using the latest HEAD build.

Good to know, glad it‘s settled!

Can‘t reproduce. When the master toggle is off, no mixins are loaded and not even the expressions are calculated. 🤔
Are you able to reproduce reliably in a clean instance?

This is actually in a dev environment... which means that all mixins are loaded unconditionally. Oops! That's my bad, I didn't realise it at the time.

(Or I guess I'll blame intellij text search for not showing me the condition...)