I have had this same problem with brand new aftermarket regulators (auto zone &napa) I went to a auto salvage yard & bought a used mopar regulator & it fixed the problem I am not saying it will repair your problem but it might be a option also I use to be a mopar flat rate technician for approx 10 years in a dealership when these trucks first came out

 

I finally put a 20 year old regulator off one of my project cars on the truck and havent had a problem since then... However... I had two bad alternators in a row... make them test your alt.

 

I don't know if it was ever addressed, and without the OP coming back, it's hard to tell, but is it possible that he never let the truck get up to operating temp and that was simply the grids turning on and off?