by Anna S..
Some more information. Mostly a more detailed description of what seemed to be broken (but not why), in case it might help someone with the same problem.
When I was trying to figure out what works and what not, I tried to preview some of the restored quizzes. Most worked, but for one of them I got an error that it was not possible to preview it because there were not enough options for a "random" type question to choose from. It was not clear which specific question caused the issue, but all were set up as follows: Choose a random question from category X that has tags Y, Z.
Deleting that particular quiz did not resolve the original error with the question bank, but when I mass-deleted all quizzes, that error went away.
Perhaps one of the categories was not restored properly and was missing questions or perhaps some tags where not restored properly. I'll see if I can find an older backup, to compare. It is still not clear to me why removing the quizzes solved the question bank issue.
When I was trying to figure out what works and what not, I tried to preview some of the restored quizzes. Most worked, but for one of them I got an error that it was not possible to preview it because there were not enough options for a "random" type question to choose from. It was not clear which specific question caused the issue, but all were set up as follows: Choose a random question from category X that has tags Y, Z.
Deleting that particular quiz did not resolve the original error with the question bank, but when I mass-deleted all quizzes, that error went away.
Perhaps one of the categories was not restored properly and was missing questions or perhaps some tags where not restored properly. I'll see if I can find an older backup, to compare. It is still not clear to me why removing the quizzes solved the question bank issue.