Each zone would get a brief 2v spike when I manually ran the section.
Is that above the 24v you are supposed to get or is it 2v total?
Checking the manual, ERR = "Electrical noise is entering the system, through the smart port wiring harness.
Check the SmartPort™ wiring harness. If the wires were extended then they will need to be replaced with shielded cable...."
Shorting out somewhere.
IF you do get 24v at the terminal, turn one zone on and see if you get it at the valve.