I have also tested without randomisation and without relevance equation but with randomisation group first, then with randomisation with relevance equation but without randomisation group and then the last time with everything in again. And it worked all the time well. In incognito and normal mode with different tokens.
We have new observations. We removed the "mandatory" status of all questions. We have still the problem that we get redirected to the beginning of the survey (1%) and only the question header is visible, but no questions are shown. Nevertheless, we are now allowed to move forward which was not possible before. So we can click through the survey again but can't see any questions. I also tried to come back and open in new incognito window and everything worked, I always was back where I left off.
If we now could see the questions again all problems were solved.
