UNFORTUNATELY, the problem reappeared after I deleted 5 students from the "classlist." They dropped from the course and keeping them in the classlist complicated uploading the grades to Blackboard Collaborate, which is the official/mandatory system to report grades at my university. In Webwoer 12 no problem, but in Webwork 15, and now without the ability to produce PDF of graded exams that I need to return to 50+ students. Fortunately, I take exams with 2 servers, and the remaining 90 students are on the old server with Webwork 12. This problem is crippling me. Online students need as much feedback as we can possibly give them. I had to take screenshots of the exams, 2 screenshots per exam, times 50, 100 screenshots. Not good.