Don't play with GM on..and only then if you really feel the need to do things as a GM.
The GM flag allows the client to see the 2 additional unsupported slots available in RoF+ clients.
To reiterate, they are not supported and will 'eat' any items you put into them (EDIT) and cause probable inventory sync issues.
Try
to induce a zone-wide spawn timer reset.
The issue with the world object showing 'in-use' by another player when no one else is around could be a bug and we can look into that.
Report back if that issue comes up again.