Proxmox Backup only at bytes

Please do a qm config 108 and post the content here in the code tag (not inline code tag!). I'm guessing you didn't set the flag.
 
Makes it hard for us to help when you are ignoring our requests to show the config files...

My guess is still that you unchecked the "backup" checkbox of those virtual disks but no way to tell that without you giving more information.