It doesn’t play weirdly, you set the position of the gun instead of welding it to the hand, so when using a different package the gun is in the same position. You can use a plugin like a tool handler to weld it into the player’s hand instead of a coordinate.
Animations always look different with different packages in my opinion and it’s pretty normal, so you may need to force the player to wear the default blocky package. Also, Please send the video of the animation so I can understand the issue better.