i have an alternate player model which uses magic to float items just in front of me rather than physically holding them, this only seems to be an issue with models that don't physically hold the item. this seems to be the only issue here and everything else about first person mod and the animation mod works as expected.
here is a link to the mod https://github.com/MineLittlePony/MineLittlePony/releases/tag/4.4.3

with the animation mod in 'f6 mode'

animation mod running normally

"F6 mode" is just turning off the FirstPerson mod, so it then uses the normal First Person for MineLP. This probably needs some extra logic to support the MineLP mod, if that is possible.