I agree, check the wiring. I had a slow crank issue on my car after changing the starter. I ran heavier wire from the trunk and it turns over like daily driver now.

Joe H. you said you had 2 failures; how did they fail, what did they do?

It appeared the amount of retard would vary. One simply stopped working. We now run a crank triggered ignition with no problems. On another car the distributor is locked, and it starts with no issues.