Clients can’t connect to the server… And no errors are available


I started several nextcloud docker images (official images with apache behind nginx reverse proxy) a year ago.
Client apps were not able to connect via password so we all used app token and everything went well.
But some time ago, an other problem appeared… The token login was not working neither…

I tested it with desktop client on xubuntu :
When I open the connection page (of nextcloud-client), the apache logs (that are redirected to docker logging) show all file the client query with error 200.
Then I connect and everything is fine for apache, only 200.
But I’m stuck in a wierd loop:
I clic on connect -> I log in -> I grant access -> I clic on connect -> I grant access… Nextcloud actually remember my login but can’t connect me…
If I use app password, the connection page loading never ends…

There is no trace of everything I just did in ./data/nextcloud.log. But when I use a wrong password, a message is appended to ./data/nextcloud.log.

What could be the cause of the issue ?
All images are in version 15 now, I updated from 13 to 14 and from 14 to 15 without problem but keeping this issue…
I will try to make my nextcloud instance more verbose.

Edit : loglevel 1 does not add any information. I will try debug
Edit2: Loglevel 0 (debug) does not print any information about loging or webdav. I got only scss or image cache errors