Sonar zoom 2 not stopping at first frame

i have a Sinar Zoom 2 that worked just fine the last time I used it.....10 years ago. It has not been roughed up in that time and lived at the bottom of a storage drawer with the camera equipment I put away. I’ve followed the instructions and don’t believe I missed anything. I just advanced 2 rolls of portra all the way through.

Any thoughts?