If you have low voltage at the pedestal, causing an increase in amps, as myredracer noted, the draw of the AC at locked rotor draw (start up) and it's fall off to the running draw, may be enough that it trips the electrical management system. If the refrigerator and the AC unit both start at the same time, the current may also be enough to overcome the settings on the management system.
Depending on how the management system is built regarding surge and circuit protection, you may also be having a problem with that. To correctly diagnose these issues, a measurement of the incoming power and the draw of the devices would need to be done. At best, when powering from a 30 amp supply, you may need to use only one high amperage device along with the fridge.
