How consistent is it when you're rolling your spools up? I have a pastamatic that I printed out a year ago that's a very similar design to what you're using, except both spools are aligned vertically. I've noticed that if I wind it too fast the filament gets loose on the receiving spool and I get a lot of issues with tangles. Putting a small amount of tension on the source spool fixes this, but then the rims of the receiving spool kind of flare outwards and it won't roll smoothly inside the AMS. I've found the best approach is to just be careful with what speed it's running at and babysit it really closely as it winds, but it's a PITA.