Pixhawk 2.4.8 (clone), AC3.2.1 works, AC3.3.3 Initialising APM when motors spin/calibration Accel

This is a Pixhawk 2.4.8, which a clone from Aliexpress, worked well. I’m new to multirotor things, just built my first copter with custom frame few weeks ago, excuse any missunderstanding. Info about the PX:

PX4v2 003D0039 3335510E 38343436
Frame: QUAD
PX4: ce602658 NuttX: 475b8c15
ArduCopter V3.2.1 (36b405fb)

As the topic says. I’ve received the Pixhawk with the AC3.2.1 preloaded and it worked fine until yesterday, when the quad haven’t remained level during take off. I had a hard landing last week, if you can call that, and rebuilt the landing gear of my frame. Updated to AC3.3.3 and whenever I tried to spin motors or calibrate the Accel, MP was constantly saying “Initialising APM…”.

Went back to AC3.2.1 now and calibrated the Accel without problems, working on calibrating the rest. Any idea what the “Initialising APM…” message means?