Backup device - Crash when trying to change path (directly after pressing the button), is there something to do?

Dear

I've been experiencing this issue since a long time, but it doesn't seem to be solved from version to version.

I would like to make a backup from my iphone to my NAS (and not locally on my computer), when I go via the backup button it doesn't work, it crashes the macos app immediately.

If I make a simple transfer without the backup feature, it doesn't give any problem or chosing to change the path and browse on my nas. So I believe there is a real issue behind the "change path" in the "backup device"

Can you let me know if there is a workaround?

Thanks

C.