MMU2S Reboots/Freezes when you Initiate Preheat  

MMU2S Reboots/Freezes when you Initiate Preheat

Ok this started with a MMU issue where it was not detecting home position and would randomly do loads and unloads middle of a print.

I sent the old Unit in and got a replacement. Hooked it up and it was looking all fine and dandy but then prints wouldnt start it just would not start the loading process. Finally noticed that it reset when ever i preheated the printer. 

Updated printer, still no good
tried to roll back MMU firmware, no good
cleared EPROM, no good
Preheated just Bed, no reset
Preheated just Nozzle, no reset and i could use MMU to load 
Hooked up a different Power supply, No good
monitored voltage, no changes
changed out signal cable, no change
unhooked PSU power detection line, no change

so far there has been no success, does anyone know or have some theories?

thanks!