I have a MT300N I got from torguard for signing up for their service. The wifi keeps disconnecting and reconnecting on my android smartphone and also on my laptop. I have operated the router in both WISP and ethernet to so the issue.
What is the firmware version ?
The latest official firmware. Tries 2.27 beta (or whatever the beta is) and the router started to make a high pitch electrical sound. I thought it may be linked to wisp and the router constantly shifting channels (hotels broadcast the same ssid on multiple channels to wisp keeps connecting to the strongest when they change for some reason.) So tried it wired and still the same problem. I did notice the router was in China power settings to set it to us and the max power went from 20 to 30.
Have you tested another power supply? Try one with 5V 2A
Because electrical sounds are not normal, so i think there is not enough power for wifi.
I was using a 2 amp but will try another. The specs says it only requires 1 amp
the power can only be 20 max. A higher value does nothing.