We have ping drops to some hAP ac routers, also experiencing intermittent winbox access. First time was fixed by disabling 5G radio. Also using lower band frequencies like 5100-5400Mhz helps because with our settings Tx power limited to 23dBm. HiBand Frequencies like 5700-5800Mhz has 30dBm Tx power. Using them causing ping drops and loosing management access. If i change antenna gain to 7dBi on HighBand then Tx reducing to 23dBm and everything works good again. Most of our routers Freq set to auto. ROS v6.42.7
Check power supplies if they show some sign of ageing.
More simply, replace one of them with a new one and see whether it improves the behaviour of the powered hAP ac.
More in detail, electrolytic capacitors in power supplies degrade the fastest of all electronic components, so the ouput voltage drops when the powered device asks for more than the average current in a short spike, causing weird things to happen. When you measure the output of the power supply unit using a voltmeter and without load, everything seems perfect, so you need to measure on a loaded power supply unit using an oscilloscope to spot the issue. So simply trying with a new one is a much easier and faster way.