I used my phone's flashlight to check for light leaks and it actually worked
Had a weird issue with my Canon AE-1 where about 1 in 8 shots from a roll of Portra 400 came back with this foggy streak on the right side, and I could not figure out where it was coming from. After burning through 3 rolls testing different things, I held my phone flashlight inside the open back in a dark closet and saw a tiny gap in the door seal right near the hinge. I taped over it with a strip of black electrical tape from my toolbox, shot another roll around my neighborhood in Portland, and every single frame came out clean. It is a dumb trick but it saved me a $90 CLA. Has anyone else found a light leak that way, or do you just send it straight to the shop?
Reminds me of when I chased a rattle in my truck for two weeks and it turned out to be a loose bolt on the skid plate. Spent way too long poking around the engine before I finally just crawled under there with a flashlight. Half the time these gremlins are something dead simple you just have to poke around to find.