In the latest Update, Mowzie's Mobs uses geckolib animations, as you know. The first person animations will always make your left hand appear. Even if it is not used.
This would be very sad, because I would love to have both mods alongside each other ^^"
Hope you can fix this

Hey, so to add to this, this issue pops up with other first person animations that other mods add. I think the easiest way to fix this would be to add a config option to disable the rendering of the left hand entirely