Hi Andi,
Yes, I have been emailing Jeff. He has been both helpful and generous. But because of distance I think it will come down to me doing the detective work.
The Problem: Slight, but noticable, up/down cyclic motion of belt on pulley.
Tried: Re-level motor pod (many, many times). Reduced but not cured problem.
Recently I decided to try again and take a new approach. Now I noticed the pulley has some non-concentric motion, a wobble in multiple directions. It's hard to see but it's there. Using digital level, I leveled the motor mount within pod. Small improvements were seen re: the wobble and belt motion but still not cured.
While I had the pod cover off I slid the pulley farther down the shaft and noticed the wobble decreased to the point where either I could not detect it visually and the belt travel improved as well. I am waiting for a new belt to arrive to rule that out. Now, I suspect two things causing the wobble, the 4 rubber motor isolators are allowing a bit of excess motor motion or the pulley is not entirely concentric. My bet is on the motor isolators. I will probably try a couple things to see if that is the case. Or I could just order isolators/pulley and see what happens, but the boat from Germany is slow.
The intersting thing is that the belt motion is cyclic to 1 revolution of the belt more so than one revolution of the platter. It's somewhat minor issue but it shouldn't be an issue at all in my estimation. I have heard from some other Raven owners saying their belts are steady, no travel. So, that's my goal.