Since the last update [Stable Update 2021-06-14] with Nautilus 40.2-1, there is a strange behavior on mounted network drives. When I drill down the folder tree (eg.: mnt/nas/alpha/beta/gamma), Nautilus steps back on this tree automatically after approx. 10 seconds per folder. It stops when it reaches the mountpoint (mnt/nas). It only happens on network drives, but not in the local folder hierarchy. I can reproduce this behavior on several Manjaro installations.
I’m running the same version and don’t see this behavior with a Raspberry pi running libreelec with sftp and smb shares running off it. Does your NAS not agree with the update perhaps?