The wiring in this falling apart (literally) crappy (ew) old (119 years) building is a nightmare. It's a wonder it works at all.
One of the best things I did for my VDSL2 connection (like you) is run a new cable directly to the MPOE. My 105 year old building's wiring was already on the outside of the house and was really old. It was an hour long project and I got a nice speed boost out of it. No more random "weirdness" on the line. If it's an option for you, I highly recommend it.
Although, really, hopefully we'll all have fiber options someday soon.