People just don't get that stim's can change. My stim has just done that, changed. For ages it was moving my thumbs thow my fingers. Now it clapping my top half fingers towards bottom part (hand) palm or a fall on both hand together clap. I have also start swing my hands around from front of my body to back.I get told to stop it. Then told you didn't use to do it, blar, blar, blar.
Mine have constantly either evolved or changed to something else entirely over the years. To me that's normal.
Mine also change all the time. They tend to be small changes to something that already exists but can be something I have never done before. To me as well that is totally normal.