Help: Node-Red add-on for Hassio runs only in privileged mode

I am pretty new to Hassio and Node-Red and am really loving the flexibility this platform offers.
I have a bunch of automations running quite well on Node-Red but seem to have a unique problem since the last couple of days.

Node-Red will not start on its own when I restart it, from the Hassio Add-On interface. It will always fail with the following error in the Home Assistant logs (Node-Red logs don’y show any output at all).

Failure linux runtime spec devices: error gathering device information while adding custom device “/dev/ttyS19”: no such file or directory
(Please note that the tty* number in the error above, differs randomly and is not always S19).

The only way to run Node-Red is to manually go into Portainer (it managed my docker containers) and edit the node-red container (the one Hassio created automatically) and set it to privileged mode. This starts Node-Red without any issues and everything works until the next reboot or restart of the Node-Red container. So basically, I have to manually start Node-Red each time, in privileged mode, to make it work.

No other Hassio containers have any similar issues and Hassio itself runs flawlessly too, with access to my USB dongles. Could someone please guide me here as to what may have caused this sudden issue.
Everything used to work perfectly until earlier this week, even for Node-Red.

Hassio runs on: Intel NUC running proxmox, with a Ubuntu 64-bit LXC container running Hassio.

Bumping the thread.
Any help would be welcome!

@ajayjohn, curious if you found a solution to this one. Just installed a Zigbee USB stick and getting the exact same issue.