Even if I’m not exactly making myself popular here:
Short interim status in exchange with Webflow Support 3 days later:
I was asked to do a restore of an older backup, whereupon I initially refused, as I am currently doing a lot of work on the site and don’t feel like blowing 1 day’s work to the wind because of a bug I didn’t cause myself.
After 3 days of being put off by the fact that the developer team still hadn’t found a solution to the problem, I imported an older backup today, as I simply have to keep working on the site and can’t wait for an uncertain answer.
Result of the restore: The error still occurs.
I then went back to a backup that was 6 days old and before the new variable modes were introduced - the same error here too.
Too bad. Next week I will consider whether to stay with Webflow or look for an alternative. Not at the prices that Webflow is now charging.