Too much timing???
Pulled and doubled checked it. Still at 18 built in. Back in and running, initial at 16 and 34 total going for a drive and will check it again....
I found the Mallory drawing of that advance mech and there are several areas that can have issues.
My drawing shows bushings in the advance weights but I have never seen one that had them. If yours has bushings they could be dirty or worn out.
It is possible the screws that hold the fingers onto the plate are loose, or worse yet, they have been wobbled out, you could have an issue there.
It appears to be something simple I believe.
EDIT: once upon a time, a customer assembled his own engine. The thing would not repeat at the track. The timing would move, but not on the first pass. It would move almost the same every time. First pass was the quickest, second pass slower, the third pass was slowest. Then it would come back to about the second pass was for the rest of the day.
He parked the car. A few weeks later he called and asked me if I lock tight the cam bolts. I said heck freaking yes I do. He did not. So the bolts came loose, the cam would move in and out and change ignition timing, not to meant ion cam timing.
Just throwing this out there because things happen.
