If you stuck with this issue when some same meshes cannot be merged make sure that there are no some micro difference it their rotations. Seems like this is a bug of unreal. When i make them equal i merged with saving collision
If you stuck with this issue when some same meshes cannot be merged make sure that there are no some micro difference it their rotations. Seems like this is a bug of unreal. When i make them equal i merged with saving collision