Are these wheels on subgrid(s) or on the main grid? Autohanbrakes subroutine turns brakes via RC handbrake property. The brakes property in wheels is used for other means, and control over it is taken from the user.
It really sounds like your wheels are subgrid wheels. In such case, for wheels on a subgrid, you need to have an RC block on every wheeled subgrid.

There are no sub grids involve as I intended the rover to be built in survival using a projector

Does your RC block orientation is correct? Block's up points to up and forward to forward?

Hey, i also have the problem that the auto-handbrake won´t work. RC Block orientation seems correct

Are your rovers build with incline? For example, when the chassis is not parallel to the ground, or when front wheels lower/higher the rear wheels?

I'm 100% certain the remote is the right way around. I've built and scripted my own drones.

The rover I've built is a large-grid rover.

I can put the wheels on my hotbar using the "brake on/off" option and that says "off" and when I press it, I see it flicker to "on" briefly but it changes back to "off" very fast. If I disable your script this doesn't happen.

When I exit the control seat the vehicle rolls. Even on flat ice I will see it roll slightly. I'd think the auto-handbrake should prevent this.

Here's the RC... It's located in my engine room at the rear of the rover but the green light is pointing towards the front of my rover.

https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=1861262813

Here are some screenshots of the rover itself:

https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=1861262774
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=1861262748
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=1861262711
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=1861262668

I don't know what's wrong with it then. I can join the world and take a look myself, but only at the weekend. Or you can upload blueprint and i will look t it that way.

Ok, so before uploading a BP and wasting anyone's time I've copy/pasted the grid (same problem on the copy) and loaded the BP into a new world... strangely this one works as expected.

The two worlds have all the same mods, settings, etc. Same starting scenario too. I even pasted the BP in roughly the same location on the same ice lake. ... but it works ... I'm at a loss.