Grinding squeeling noise on my Singer Touchtronic 2000?

I have a 25-year old Singer Touchtronic that started a grinding/squeeling noise last week. It still works, but it makes an intermittent grinding noise going forward. When I am sewing it sounds as if something is dragging or grinding inside.
(It makes almost no squelling noise when sewing in reverse. )
Sometimes it will run silently (for a few minutes) and then start squeeling again.

Can you tell what is wrong and is it worth fixing? If not, any suggestions on a sturdy replacement model?
Thanks for your help and advice.
The last repair in 1987 (electronic panel) cost $100 for an electronic part.
I sewed thousands of yards of fabrics on this workhorse trouble-free and have invested in lots of attachments.