Why does Nissan Hardbody switch off when I reverse

Nissan Hardbody, 2.4, 16 valve double cab, 2003 model. When I reverse, especially bit faster than normal, it switches off, or jerks and back fire then cuts out. Have to revers very slow for it not to cut-out. No problem when driving.

The diff, gearbox, prop and motor has been checked and tuned/repaired. Diagnostics was done, all ok.

Please help