I'm getting these as well periodically. Best I can tell is that they seem to happen when my backup share (over Tailscale) starts seeing some issues (possibly packet loss somewhere?) and "du" or "df" (can't remember) starts failing to that remote share. But once it happens there is no recovery - even when the remote Tailscale node recovers, which I can see from my laptop on my same home LAN. The main issue I start seeing is that my docker apps won't restart and throw an exception. The only way to recover Unraid is a reboot.
Yeah, I know the Tailscale container states that it is intended to provide remote access to Unraid only (not any gateway functionality).