I believe this bug has occured in the current build with the Arkesia (1st annivesary skins) which WASN’T available for Striker and Gunslinger, as those classes didn’t exist back then in the Korean Version.
However in the Western Version that play, they decided to let us use it, which was a nice change honestly. However, the current build has broken the model rigging for sure. An example are these 2 gifs I recorded, this was EASILY fixed by changing into a different skin or disabling the skin showing on the character.