Every single weapon from the RWBY mod gets thrown into the offhand upon entering combat mode, which messes with the animations. No other mods I've tested have had this issue. I have the build mode player model disabled in settings. Otherwise, everything seems to function as normal with RWBYM.

Forge 14.23.5.2847
Epic Fight Mod 2.2.4
RWBYM 4.6.7

Note from the dev of RWBYM, "Our weapons count as bows, so it could be because of that."