Android App requests wrong url's

Hi guys,
I have the same issue with Nextcloud 15. Did you solve it ?
For me, everything is working, it is just reporting those errors.
However, I want to use fail2ban apache_auth and this immediately bans any good client, because even the good ones, which are using the right password and are working fine, are producing those errors.

Are there any hints? Is it the password protection of .htaccess of the webroot ?
Any hint appreciated.
Thanks, Joachim