Are you inserting into a PoE injector? or locally plug jacking it?
One thing we found was if we had two batteries in Paralle to give 12V the drain of the battery brought the voltage down too quickly and the devices dropped. When we had them in series to double the voltage to 24V then we had a bigger voltage range before it dropped. We were mounting on a pole with a Solar panel and we were PoE injecting the power.