Recently went through box of my mom's stuff from the 70s/80s and she had a Canon FTb along with some zoom and macro lens for taking photos of her jewelry. I've run 2 rolls of Kodak Ultra 400 and the biggest thing to improve is me. The small thing to improve is that the mirror will get stuck in the up position at shutter speed 60 and sometimes at 125 and 30 (one in ten).
I took off the bottom and everything looks pretty clean. Cleaned up some of the old grease with a cotton tip and some alcohol and added a very very very small amount of TriFlow. I've replaced the light seals and the mirror foam to no change in mirror performance. The mirror goes back up when going to the next exposure.
Video of issue: https://youtu.be/VZzx1yYxnKE?is=Il4OZr0fUpXqfmRa