Thanks for your input. Actually one of the features I love about this machine is that there is no need to pull up the bobbin thread. You sever it after sliding the bobbin case closed and it automatically gets taken up and ready to sew. As I explained to dolphyngrl the bunching occurs unexpectedly, as when I have sewn three borders on a quilt and am on the fourth side.
The ominous grinding sound starts and that's it - the only fix is to take the spool of thread off and re-thread it. Then it will work fine for a short or long time, depends. NannyQ

I have this machine buT can't answer your question, good luck. I have had many problems with mine, my dealer has been very good and has replaced many parts on it and we seem to be be getting there but your problem is a new one. it sounds like a threading problem

I just bought the 2.0 and love it. Couldn't justify spending the extra on the 4.0, which I really liked as well. Mine is doing just great. Still sorry that my 7550 bit the dust :{

I also have the 2.0 and notice most of my problems are caused by my threading or the way I have my bobbin in. Sometimes I just have to walk away for a while or sometimes I just change machines. I have 4 Pfaffs and a featherweight and try to use them all off and on. Love them all. :D

I am replying to my own message sent in March in order to send out some info. Recently stopped by my local dealer and mentioned the problem I was still having with the Pfaff. Only now, after attending a seminar they have learned that there is a quirk in some of the QE4's that causes the thread to bunch up after sewing along nicely for varied periods of time. I found the only home remedy was to remove the thread, rethread the machine and remove the bobbin and put it back in. The shop was able to repair the problem finally with the addition of some kind of gizmo inside and I was told the newer models already have the gizmo attached. Just wanted to follow up... so far, it's working great!