Ansmann W3 ABS/reverse prob's

[soane]

I've just installed this 2.4 system into my Ansmann and whilst fiddling about with it, I can get either the ABS to work or reverse but not both - the instructions state to brake (ABS on), back to neutral then reverse as normal. In practice however, the ABS is on all the time and the car stutters in reverse. Switch off the ABS function and it reverses fine. Strange