Yea mate I have a Suzuki df175 with gmi 20 and a 751xs and 70dv
i had the same problem and it even caused me to run out of fuel nine miles of the goldy
you need to do a update and also mainly rely on your main head unit as it seams to freeze when traveling.
mine I noticed froze once from mud island to the cape I think it was about 25-30l when I came of the plane it stayed at 4200 rpm and I had to turn the power of to reset it....
now on I only insert the fuel into the 751 and it is always accurate and the gmi20 is out 3-10l every trip
cheers Scott. I hope this helps