I hung the unpainted door in the track so I could check its travel and to have a convenient way to hold it for painting. It "snapped into" the wheel hanger assemblies. Now I want to remove the door so I can do the drywall. I've "unlocked" the white locking tabs on the hanger plates mounted on the top of the door, and given the door several good "tugs," hoping to "unsnap" it. No movement. How do I remove the door?