Can't install profile

Each month I collect the students' iPads and resync them using Configurator. All software is up to date. The student profiles restrict installing apps, so I remove the grade-level profile first within the settings of the iPad itself. The supervision profile always remains. I have found I get too many errors if I do it by simply unchecking the profile box and refreshing on the screen.

After this is done and I go to refresh in Configurator, about 1/20 iPads ends up getting stuck on "Supervising device" and then gives me the error "Can't install profile." When I go into the settings on the iPad, the supervision profile is suddenly gone too! I have been able to successfully get it to go after a lot of trying things in a different order, quitting Configurator, restarting the iPad, etc, but there doesn't seem to be any pattern in how to fix this, and it always sets me back about an hour just for one iPad. The other weird thing is that I'm starting to realize it's the same kids' iPads that do this every time. I even unsupervised one of them last month and set it up as a new iPad, but it's still giving me this error this month. Any ideas?