Arceus Plate glitch

If you obtained Arceus in the post-game, and you give it a plate instead of the crystal piece, the moment you remove it, Arceus remains that type(of the plate). As a result, the crystal piece doesn’t work on arceus after. Is this supposed to happen? Please help.

No, it is a bug.

happens with giratina aswell with the griseous orb

thanks for the help

This might be tied to the bug that cause pokemon not reverting from form changes it should be fixed in the latest patch.