I would suspect the power supply. Are you using a power supply capable of supplying the correct voltage and current? Sounds like when the wireless card starts transmitting, it draws enough current to drop the input voltage below 10 volts.
I would remove the wireless card and boot the router. Then check
/system health print
See if the input voltage is close to 10 volts.
ADD: I just got a new R52Hn radio, and the data sheet shows it uses almost twice the power (7W) of my 433 (4W) when transmitting in n-mode. Your “/interface wireless” setup shows you have 3 radios.