Distributor advance

I recently had a hard to diagnose (and possibly unusual) problem with the electronic MP distributor that came with my magnum crate motor. The symptoms were:
1) unstable timing-timing would not stay in proper adjustment, resulting in....
2) unstable idle, poor performance, stalling, backfiring, etc.
The problem gave all the symptoms of faulty carburetion (manifold leaks, clogged jets) yet no apparent faults with the carburetor.
I went to the most apparent source of the problem-the distributor. I found that the split pin which holds the reluctor in position had worked up to a point that was allowing the reluctor to turn on the distributor shaft! I discovered this by accident while holding the reluctor and turning the distributor drive gear. Needless to say, after correcting that condition and reinstalling/retiming the distributor solved the problem.
As they say-what are the odds?