incompatibility with supplementaries 1.4.8
version: 18.2.4

crash-2022-08-22_18.20.59-fml.txt

net.minecraft.ResourceLocationException: Non [a-z0-9/._-] character in path of location: supplementaries:entity/flags/greekfantasy:spider
Supplementaries is trying to make a flag out of a registered banner pattern, but did not account for modded banners.

ok, I will try to send a message to Supplementary's developers

fix set in the last version of Supplementaries.