Front AC Not Cooling

Where is your thermostat for the unit that is not cooling? Mine is just outside the door to the bedroom where my second unit is. If the bedroom AC is set lower than the main AC / Thermostat, it will falsely cause the thermostat to think the room it is supposed to cool has cooled off and will not cycle the AC unit the thermostat controls. Try either raising the temp on the second unit (which you say is cooling to 70 degrees,) or turn it off to see if the other unit will cool things off. Perhaps a bit basic, so forgive if "it goes without saying" the thermostat is not too close to the one that is cooling.
Thanks
Tim