your beam is not out far enough to keep the chains parallel to the work surface. you set the chain height on the sled by the ring height so when the chain holds the sled, the sled lays at 15 degrees. then you put the beam out from the work surface enough to keep them parallel to the work surface otherwise when you get to where the sled is close to the motor, it will try to shift gears like on a bike. You want that chain striaght with no side pull. I think I showed adjusting the beam in one of my videos, but it probably wasn’t super easy to follow. I’ll refer you to this alignment diagram:
and this sled hang picture (#4 is desired):
