Help! Machine issue: backstitch bunches up
Hello! I have a Juki TL98Q that is approaching 20 years old. For a while it has had an occasional issue that the fabric bunches up when I try to back stitch, instead of moving backward smoothly. I recently had the machine serviced due to another issue and now the backstitch bunches up almost every single time. I don't want to take it back to the same repair shop, even though the work is 'guaranteed'. Does anyone have any experience with this issue??? As far as I can tell my options are:
A. Spend roughly $125 on parts I can replace myself, throat plate and a couple of other things, that may fix the problem.
B. Take it to a different repair shop and spend more money on it.
C. Just buy a new machine. This one cost $1000 nearly two decades ago, perhaps it's useful life has come to an end.
What do you think???