Check out the WindRace thread, I've just tested the Pixie3 with both the WindRace app and GPSLogit recording with the display off and there are no gaps or spikes in the logit data. As soon as I turn WindRace off, the gaps in the data appear again. I've emailed Manfred, so with any luck he can do something with logit.
If not both apps running allows the display to be off, to conserve battery.

The WindRace app, exports in .gpx format so doppler data isn't available.
It has a nice doppler report but it doesn't give us all our divisions , so at the moment it isn't a logit alternative.

ALL HAIL TO COREY!!!!!!
He was adamant that when he uses the Pixie with his wing suit, and display off, he had constant speed talk and no gaps in the data.
So we compared set up yesterday and he has, Settings/Display/Sleep, set to "never". The default is 1 minute, took the Pixie for a ride today with the display off, and solid data, no spikes.

We both also had, settings/Battery management/ Saving mode, set to "off", not sure what effect this has.

WOOOPS I've got no idea what's happening, but went for another ride, and there's hardly any data at all. This is doing my head in. so I'm going to have a rest from it for a while.