As angelozip says it is possible but have had this alot way back in time, if you run an Hand held like my old Etrex or even a Etrex 30 you actually cover the Antenna while in your hand so you get a temp lack of signal so short loss of tracking, it even happens when I use my PDA moving Map device and it's not lack of Signal but SA "Selective Availability" set by the Satellites, so it's info your device gets confused and has little glitches "heck we only pay a few 100 Dollar's for our GPS's and you expect them to be perfect Hey.

But don't think that "pay a few Grand" and maybe you have some rights but we don't, been in Electronics to long and know just how much designers and Company's Skimp on design and Software.
Live with it Guys and learn how to download your data and how to Edit the Results.
Mags.
I know where I am Do you?