Issues with ESC control protocol on first build

Hi, just but my first rover together and had set MOT_PWM_TYPE=4 in accordance with the documentation here : The ESC starts making angry beeping noises and the throttle behaves strangely. So I hook up the scope and I’m clearly getting a signal at around 50KHz. Presumably one of the OneShot or DShot protocols ? I assumed I was going to get a 50Hz PWM signal with some behavioural change in the throttle. Is this how it’s supposed to behave ?
Documentation for copter here says it’s DShot150. Can some one clarify ?
27/12/2022 12:31:58 : Pixhawk1 003A0040 30395109 36373532
27/12/2022 12:31:58 : ChibiOS: 38022f4f
27/12/2022 12:31:58 : ArduRover V4.2.3 (2172cfb3)

What ESC do you have.
basically 1500=neutral, 1000=reverse, 2000=forward
I’ve reset MOT_PWM_TYPE to 0 and put the throttle on the elevator so it centres and it kinda works until I disarm and then it goes into reverse, also mission planner is complaining about it not being neutral during arming (I’m forcing it to arm).