USB disconnect during work

I have USB externall drive connected over USB 2.0 at Turris 1.0
When Turris boot I see device connected at defined at fstab to /mnt/usb1.
At this USB are LXC containers and one is Nextcloud. When I copied my files (1.5 TB) to data folder (not at this USB) everything works. Then I start scanning files for Nextcloud shared folder and after short time scanning failed.
Reason: Turris disconnect USB.
Device is completely disconnected and can’t be connected again. Only reboot helps.
Any idea what can happen?