Either the camera or scanner needs a spring clean, or both. The black splodge is reminiscent of something dangling in front of the film, if you are looking into the camera with the back open it could be in bottom left of the shutter gate somewhere. But there is a lighter fibre at the bottom and a spot in the same place on both photos as well and most likely the scanner.
If not a fibre the black splodge does change shape slightly and if it moves gradually across the frame in other photos (which we can't see) it may be contamination from the rollers when it was processed.