740 autobox problems - help!!

[bluem5]

My e38 740i keeps on finding false neutrals and computer shows
auto trans - fail safe mode - it thens stays in 1st gear.
Can clear the problem by switching ingintion on and off many times, sometimes the fault comes back in minutes or else after a week or so.
The computer codes read out speed sensor - throttle switch, but my
local specialist is a bit vague about what is needed.
Ani ideas out there ??