Sort by start date not working?

Sort by start date not working?

Hi,
since the last wordpress update on my sites all events are not listed by ascending start date anymore. We use this tool with different filters (by category) on various pages.

Here's an example:
https://verein.writersstudio.at/alle-termine/ -> sorted may be by date but in wrong order (descending instead of ascending?)
https://verein.writersstudio.at/schreibtreffs/terminueberblick/ -> sorted by ?? but not start date.

Not sure if relevant, but here's additional info:
* I use elementor, so the issue may be connected to the widget? When I change the filters to sort events from i.e. ascending to descending, or sort by create date instead of start date: no change is visible, no reaction to the change.
* I cleared both the cache of the website and my browser chache, on one page this fixed the issue, on the two mentioned above no improvement or change.
* the one where the issue first was there but disappeared with clearing the cache was set to display only 3 results. The ones with the issue are set to display 12 results - but even when I change it there to only show 3 the sorting mechanism still doesn't work.
* the sorting order changes if I display the widget with or without filters. However neither version actually sorts by event start date.
* if I make a new widget (to avoid carrying over some issue an existing one might have) I get the same problem.

Is this a new bug? Can you suggest any way to fix this, is there something I can do? It is very irritating for our customers, and we rely on this tool a lot.

TIA,
Anna