Throttle limited when telemetry connected

Hello, I appologize from the start if this was discussed before.
I have an ARF Quanum Venture on which I’ve put an APM 2.6 FC with a 3DR telemetry and MAVLink OSD.
The problem I have is that, when telemetry is connected I cannot rise the throttle level above 10-12%, depending on the flight mode. Even with the stick in max position the value stays the same.
After I make an ESC calibration the throttle is not limited but I cannot connect via MAVLink anymore, hence I don’t have the values on the OSD (it only shows “No MAVLink connection”)
I’m stuck!