I had problems with my Makerfarm similar to yours the first few months I had it. I solved the pull tension issue of the spool by setting it up with bearings. It spins with almost no effort at all. However, that did not resolve the problem completely. I was using the hex hot end and actually went through two of them over about four months. I then bought an E3D v6. I drive it with a Bull Dog Lite and my problems have all but disappeared. Now, if there is a jamb it is usually associated with printing a very small part or portion of a part where the retraction happens to frequently. On those rare occasions, I just turn off retraction.