When I use the "Randomly assign reservations" option, and click on "Assign reservations", the UI does not provide any indication that the action is in progress. Considering the fact that this action can take a couple of seconds to complete, it becomes tempting to click it again, since it appears as if the first time didn't register, and that can cause weird registrations to be created. I'd suggest this button be disabled upon clicking, or at the very least some UI indication that the assignment is in progress.