I haven't seen bad potting resin having any effect on whether the ECM works or not. I've had brand new ECM's (both Mopar and aftermarket) leak resin right in the box sitting on the shelf. I've had nasty looking used modules missing most of the resin that worked fine, and as you found out, I've had perfect looking new ones not work at all. If you're going to race, get and MSD system and not worry about it.
