I bought a used old Thermolyne multi-stir which heated but would not stir. Both stirrer motors are connected by a cog belt which was brittle. I called the company (which more Bees ought to do) and requested the tech info/parts list. I oiled the motors, repeatedly over about a week, top and bottom, with the machine right side up and upside down. The new belt i ordered arrived a few days later and that stirrer has been my best friend for the last two years.
Originally I thought I might get one working stir motor at best, but TLC, 3-IN-ONE oil and a $20 part brought that stirrer back to life. It works better than the new one I bought as back up.
Anyway, dont give up. Oil those shafts!