Honestly, I had a Canon AE-1 mirror lock up on me mid-cleaning yesterday.
Tbh, I was in my home shop and the mirror just stuck open after I'd removed the lens. I used a tiny bit of isopropyl on a cotton swab on the hinge post, which freed it, but I'm wondering if that was the right call. Has anyone else had a better fix for a sticky mirror on these old SLRs?