Test done. No issues. Before flight I changed parameters:
from: SERVO_DSHOT_ESC=0 to: SERVO_DSHOT_ESC=2
from: MOT_PWM_TYPE=DShot150 to: MOT_PWM_TYPE=DShot600
Hope DShot speed change haven’t influenced target of test you wanted me to do.
Anyway, motors spun with both DShot options but 12min flight test was done with DShot600 setting.
Question: Should I stay with SERVO_DSHOT_ESC=2 for regular flights? Or revert it to 0?
This is with the new firmware I posted? Please can you also try dshot 150 to verify that still works?
You will find that if you set SERVO_DSHOT_ESC back to 0 it won’t work again for you
Yes, test was with new firmware you posted 3h ago - 4.2.0
DShot150 still works - but just short hover over floor tested.
I set SERVO_DSHOT_ESC=0 and issue returned → motor 4 could not arm.
I set SERVO_DSHOT_ESC=2 again and issue disappeared 
We’ve released Copter-4.2.1-rc1 with at least some of the fixes from @andyp1per. I wonder if you could retest using the official version downloaded from MP or QGC?
Now, I’m not tracking in detail which issues are fixed and which are resolved so apologies in advance if this ends up wasting your time a bit. I suspect @andyp1per will correct me if I’ve got something wrong.
I’m not sure that I can find Copter-4-2-1-rc1 release.
Should I search in beta firmwares? I believe that Copter-4-2-0-rc4 was available via ‘All options’ but maybe I’m wrong.
Just short arming test. Results are like in my post above, no change. Works ok with SERVO_DSHOT_ESC=2. When set SERVO_DSHOT_ESC=0 issue appears.
Thanks - this is the fix
Copter-4.2.1-rc1
With SERVO_DSHOT_RATE=4
MOT_PWM=4 (Dshot150) no motors span on multiple attempts
MOT_PWM=5 Dshot300 all motors span on arm
MOT_PWM=6 Dshot600 1st attempt, no motors span, subsequent attempts 3 out of 4 motors span
Did you set SERVO_DSHOT_ESC=2 ?
Copter-4.2.1-rc1
With SERVO_DSHOT_RATE=4
SERVO_DSHOT_ESC=2
MOT_PWM=4 (Dshot150) no motors span on multiple attempts
MOT_PWM=5 Dshot300 all motors span on arm
MOT_PWM=6 Dshot600 1st attempt, no motors span, 2nd attempt, all motors span, rebooted, worked first time
MOT_PWM=7 Dshot1200 - not a flicker
So Dshot 600 seems to be working fine now, but no dice on 150 or 1200, not that either of those worries me!
So this is the behaviour we saw when you were testing originally - so that’s good, that’s what we were shooting for.
I have been unable to either repro the dshot150 issue or figure out what we could do differently so it probably is what it is for now
Hello , can i have a details about TradHeli internal error during takeoff fixed !?