Two rockford Fosgate amplifiers shut off

So long story short, party bus, 4 rockford T2 15's, 8 rockford p3 6.5 ,2 1000bd power amps, and 1 4-channel amp. Pioneer head unit. The bus is a 24 volt system, amps are ran off the 12 volt side, had some issues with them going into thermal, shutting down and restarting after cooling off but I was unable to verify this myself. I could not get them to overheat or shut off. But I did notice voltage drop of about 3 volts so I added an extra 160ah battery behind the amps, to negate any low voltage issues that may cause them to overheat. I played the system for almost 3 hours under the loudest hardest bass I could find, super low and high bass tones to draw most current and voltage was steady never dropping below 12.9. I didn't want to add too big of a battery to one 12 volt side for fear of off-setting the charging system, the alternator is 24 volt and charges 2 big 12v batteries. The issue I'm having is both of the rockford sub amplifiers are shutting off after playing for some time, but come right back if you reset the radio. I was on a run, drinking at 2am so I wasn't able to check voltages during the event, but I was able to hear both amps quit same time and bass. 4 channel never quit. They all have the same remote wire bridged off of a 40 amp relay so I don't think they're loosing remote, and I find it hard to believe that they both overheat exact same time. But with the size of the batteries and now an extra one I find it hard to believe there's low voltage as well. Any input would be appreciated. Knowing is Half the Battle

With that kind of power level for subs noticing the first amp drop out due to protection would be negligible, 2nd amp drop out would be very discernible as all remaining bass is being lost. Thermal soak takes time to build until threshold is reached. As long as the heat being generated is greater than the heat escaping the given space they will eventually shutdown due to thermal protection. Would start with adding a fan to exchange the air in the space, Especially if the space where they are installed is not well ventilated. Then a fan to move the air over the amps would be beneficial to lower the amp temps. Amps use passive cooling to expel the given amount of heat they generate. Which requires that the surrounding air be cooler than the minimum temperature required to cool the amp. The amount of heat any given surface area can dissipate is directly tied to the air temp differential. As air temp gets closer to amp temp the amount of heat that can be dissipated goes down, the hotter the amp gets the more inefficient it becomes, the more heat it generates, and this continues until protection temp is reached. You could use a remote thermal probe to monitor the temp in the amp space to see what the temps are.