This bug happens when ever you enter or leave the swimming animation when holding a crossbow which is loaded! The right arm (even when holding it in the offhand) will spin around for a second before returning to normal!
MC-260689
Arm spins when swimming with a loaded Crossbow in your offhand
Resolved
Fixed
4
(Unassigned)
Confirmed
Platform
Important
Player Animation
Animation
1.18.2, 1.19.4 Pre-release 3, 1.19.4, 23w14a, 24w05b
1.21.1
Retrieved
Can confirm in 1.19.4 & 23w14a