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JES2727:
Find an access point where you can put a clamp-on ammeter around just the two hot wires to the motor. Do this for each motor. Both should read essentially zero. If you can not get around these two wires, then measure each hot wire individually. And as you know they should be the same. The point here is that the measurements are being made where there is no other load on these hot wires except the motor. If the currents do not balance, then there is a shunt path to ground or neutral beyond this measurement point.
If you can establish that the currents to the motors are correct, then you have to look for a shunt path between this point and where you previously measured current. That shunt path will somehow get to either ground or the neutral somewhere.
Relay chattering may imply low voltage, a badly designed alternating relay, loose connections, or some other abnormality.
Do some voltage checks at various conditions. Such as start-up, use min-max hold for start-up, and maybe both instantaneous and min-max for continuous run. If you are short of meters use incandescent bulbs to look for start-up problems. Three to five volts change at 120 V should be easy to see.
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