I had this problem with my Addams as well. I did everything pinwiki said to do and it kept happening ( I never thought to try tightening the voltage regulator, but I may just try that sometime soon) even though I had 5.01v at C5 and 4.96v at the MPU. If your problem is anything like mine you wouldn't get a reset by just double flipping ( I had a friend do nothing but double flip for a good two minutes and no resets, I had the ball in my pocket during this test, and my meter on the MPU. The lowest reading I got from the meter during that was 4.87v.) While not great, it is still above the reset threshold. So I figured that the problem was solved and the game was good to go. Nope, ball one I get a reset. I think that a sling hit combined with a double flip was somehow causing the reset even though the 5v line never dropped below 4.8 volts (I believe the the watchdog chip only resets at 4.6v)
Long story short, I put a WPC power fix board in the machine and have not had a reset in three years.