Is the character with the missing hands wearing the Tarnished Charm (Neck slot item, The one that gives you better death saves)?
Equipping that charm causes the character wearing it to have their arms disappear from the elbows down. It doesn't seem to actually affect them, but can potentially make some cutscenes kinda strange.
Tks that was the cause in my game. Removing it restores the characters hands, also had each other party member try it on and off and the same results.
