It sounds like a shutter problem.(posted 8223 days ago)
I'm guessing that the sunny outdoor shots were taken at a higher speed than the indoor ones. In which case it could be due to the shutter curtains closing or narrowing before the first curtain has run the full width of the negative. This will give unexposed sections on one side of the frame, and can be caused by the spring tension of the blinds being out of balance, which is a fairly cheap and easy thing to fix, or it could be caused by one of the tapes coming unstuck from the shutter blinds. The latter problem is a lot more expensive to fix. It causes one of the shutter blinds to lean to the top or bottom, instead of running true. If your shutter looks a bit wrinkled when it's closed but not tensioned, then this would be another strong indicator that the shutter's in need of attention.