Hi. I have APM 2.8 which works well until I plug in ublox NEO-6M-0-001 GPS. I did not tried other GPS so far. Click here to see video. Thanks.
It might be that your APM of GPS is broken. Where did you get your APM? It sounds like it’s some Banggood or something else as there are no officially made APM2.8. Last official APM released by Ardupilot project is version 2.6.
There might be that some of the shotky protection diodes have broken on your board. When did this start to happen or from the beginning?
Have apm 2.8 and I was having the same problem. I switched the power wires from gps to apm(black to red, red to black) and now everything works perfectly