I've rebooted a couple times but I stopped doing that because nothing changed
A couple of time could be any number. The fact is that is the worst thing you can do with a VDSL connection as DLM would see it as a fault. That said your noise margin is excessively high which would support too many reboots or as @Keith_Beddoe says a problem with your line. As you report the QLT as being silent you are going to have to bite the bullet and call it in.