The water box will always have some water in it. It is a can that only can be emptied through exhaust back pressure.
It is normal to have water in it.
As for moving it back. Been there done that. You need to break it loose, for me that came from rotating it.
Also be careful putting it back that the bottom corner does not come in contact with the hull as it will wear a hole in it and then you get hot water in the bilge.
Cheers.