I had these warnings about turret and barrel
LogPhysics: Warning: ForeachShape(Convex): [/Game/Tank/tank_fbx_Barrel.tank_fbx_Barrel] ScaledElem[0] invalid
To fix it I had to remove collisions (complex and simple) on the turret and barrel meshes. Then I have added a box simplified collision. (Collision > Add box simplified collision).
hope that helps good bye