Sleep Paralysis Scratches?

So my friend has recently been telling me about him having sleep paralysis. He's had it since he was 3 years old. According to him, his mom has also experienced sleep paralysis and seen some paranormal stuff like ghosts. Back to the point, he says that every time he has one of these sleep paralysis episodes he wakes up with scratches. Like in the morning he checks, physical scratches, not just a hallucination. I told him it could be just him scratching himself, his surroundings, etc, but he says it happens every time. I told him he should record himself to see if he captures anything, but I find it odd. Has anyone experienced something similar to this?