Group folders won't open in the nextcloud app

Hey everyone,
I have a problem that my users can’t open group folders on the nextcloud app. When they try to open a folder the app crashes and this comes up:

java.lang.illegalArgumentException: Comparsion method violates its general contract!
at java.util.TimSort.mergeHi(
at java.util.TimSort.mergeAt(
at java.util.TimSort.mergeForceCollapse(

more Errors…

My cloud is running on 18.0.3.* What do you think what is wrong?

Thanks for help!

Nextcloud v.13?
That’s quite old… End of life over a year ago…

Maybe this can help

Sorry not 13 of course 18.0.3. Sorry my bad.