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