Motor balance error even no motor connected

I recently done simple test with Pixhawk 2.1 running on Copter 3.6 frame ware s/w without connecting Motors/ESC.
I just want to ensure that servo output for motor 1 to 4 synchronized with throttle output.
Servo outputs on Motor 1,2,4 on MP kept increasing even RCIN1(Roll input) ,RCIN2(Pitch input) ,RCIN3(Throttle input) ,RCIN4(Yaw input) have constant values.

I did radio/acceleration/compass calibration multiple times, still same results.

Pls advise what has gone wrong and what should I do to rectify this.

It doesnt work as you expect while on the bench, rc inputs dont directly map to rc outputs. The flight controller will be trying to lift off and stabilise.
Connect motors and ESCs, hold the craft fairly level WITHOUT props, get someone to arm it in Stabilise mode and throttle up a bit - see which motors spin faster and slower when you tilt it sligthly.

Thanks shawn for your prompt response. I was away from country for last 3 months so I couldn’t test it.
Now, I am back to action. I tested on bench without motors or ESCs connected to flight controller(Pixhawk black cube 2.1). All the calibrations are done successfully. Flight controller is placed in flat and level. After ARMed, I have noticed that Servo Output on mission planner. I expected all motors output should be same as flight controller is in flat and level.But servo output for two or three motors(out of 4) are not in same and keep increasing . Can you please me help me how can I correct it. Please advice me where I made a mistake.

this is expected, you cant read very much into what it does when not flying. Because you never get it exactly level the Integrator (the I in PID) builds up and you see a large offset in motor outputs.

Thanks Peter for quick response. At the start up, after ARMed , one or two motors spin too fast before copter lift up. it caused to damage the motor or ESC due too much power distributed.
Is there any way to control servo outputs manually(to give equal power to all motors) untill copter lift up

you had props on? If it tips over with props on most likely your motor ordering/rotations are incorrect

Thanks Peter…I will check the direction of motor