Can tuning ATC_ACCEL cause a flip - crash?

Morning, We have a largish Quad coaxial.
TOW no payload is 20kg
TOW with payload 25kg
Flown the aircraft several times with payload and was having altitude hold instability, was wandering ± 4 meters up and down, with and without payload.
Tweaking parameters including using GPS as altitude improved thinks.
Had a good flight without payload. before adding payload changed ATC_ACCEL: -
|ATC_ACCEL_P_MAX From |27400 to |20800|
|ATC_ACCEL_R_MAX From |27400 to|20800|
|ATC_ACCEL_Y_MAX From |11700 to|8880|
Looking for a docile like flight characteristics.
As soon as I took off with payload the aircraft flipped over. This was very quick.
No idea what happened.
ATC_ACCE changes the FEEL not actual Accel rate, it this correct or could this be the cause of the crash.

Any idea please?

Do you think it is because you are using GPS for height issues?

how do you derive the MOT_THST_EXPO,0.2? Are you using Alpha ESCs?
PSC_ACCZ_P,0.5, you should set to MOT_THST_HOVER.
why is SERVO9_FUNCTION,36 == motor 4?
AHRS_ORIENTATION,8, Roll180, double check.

LOIT_BRK_DELAY,1, I suggest going lower.

there is a recommended way. I used a Lua script with an RC button to select before arm and it also updated the Z-CG.

Thanks for looking at the FL.
Do you think it is because you are using GPS for height issues?
No it flew very well with this setting. Altitude hold was more stable than Baro.
Are you using Alpha ESCs?
Yes these are Alpha ESCs.
why is SERVO9_FUNCTION,36 == motor 4
I has an issue with ESC 4 not initializing when in the usual port 4, (Sometimes)
AHRS_ORIENTATION,8, Roll180, double check
Yes this is correct.
there is a recommended way. Very nice idea.

I am starting to think, ESC 4 stuck on. This would explain a lot. It could also explain the historic altitude instability. However I would have expected to see Yaw issues.
I tested the ESC and if it loses PWM it takes nearly a second to shut the motor off.
Sometimes the ESC does not initialize on a cold start. Power off and on usually sorts it out, but perhaps it failed in this flight.

Jai. I am amazed how quickly you picked up an all these points. very impressive.