There are issues with film that can cause problems. Scratches, overexposure and other troubles can damage film and cause things to appear that are purely mechanical and not supernatural in any way.

Digital equipment isn't free from issues of its own. I once accidentally set off my own digital camera, shooting an image without my knowledge. Later, when reviewing my shots, I came across that image and was shocked at what I found. But later, after retracing my steps, realized that I must have set it off while taking it out of it's case. Although, the one thing that I can't explain is why the camera was on while I was taking it out. It hadn't been used in weeks and if it were on, the batteries would have been dead, for sure. Still, it must have been something like that.