As I see it, there is two minimum options:
1/ Buy a replacement saw.
2/ Obtain a set of new brushes and try them, if no success, go to 1/.
BTW, if you have a job obtaining brushes, I have had luck in the past contacting Helwig-Carbon, they make replacement brushes for industrial machines etc. and may have something on the shelf.
Measure the present size/width's with a vernier scale etc.
I had one with misleading symptoms like yours, turned out to be bearings !
1/ Buy a replacement saw.
2/ Obtain a set of new brushes and try them, if no success, go to 1/.
BTW, if you have a job obtaining brushes, I have had luck in the past contacting Helwig-Carbon, they make replacement brushes for industrial machines etc. and may have something on the shelf.
Measure the present size/width's with a vernier scale etc.
I had one with misleading symptoms like yours, turned out to be bearings !