False "dead" motor not spinning

Hi guys,
I’m new to the hobby and I’ve a diy drone that i’m working on, using the APM 2.6 on 3.2.1 Firmware.I’ve calibrated my ESCs,and all the manual calibrations that have to be done (radio,accelerometer,comapss,etc), and am able to arm my quad.
However, whenever i rev the throttle, i only get 3 motors spinning, and am not able to get all 4 motors spinning.Although the “dead” motor does not spin when i rev the throttle, when i increase the yaw and pitch on my transmitter, the “dead” motor starts spinning.Furthermore, when i pick up my quad (props off) in stabilize mode and tilt it manually, the “dead” motor starts spinning to correct the quad, as i assume it is meant to do.
I’ve looked on google for people with only 3 motors spinning and only came across ESC calibration issues , where 3 motors slowly start up together while the 4 one does not. I do not think that this is my problem as i’ve calibrated my ESCs (all together) , and the 3 working motors spin immediately instead of slowling starting up 1 by 1. I’m not sure if the people with the esc calibration issues on google have the same issue as me where the “dead” motor is able to spin when they apply yaw and/or pitch as they do not make any mention of it.
I would appreciate any help rendered, opinions given to help me get my quad up into the air.
P.S I’m trying to get my logs up but can’t seem to figure out how to do it, if someone could kindly direct me to a page with instructions, or tell me how to extract and upload my log giles, and how to analysis it, that would be great!.

When you did the esc calibration, after it set the low throttle point did you test the response by moving the throttle? or did you just unplug straight away?

After the esc calibration is complete I move the throttle to check that all 4 motors spin up at the same time/rate as this checks the components because the apm/pixhawk is technically removed from the system. If they don’t I try re-calibrating or moving esc’s/motors around to see whats not quite right.