I have the MediaTek MT3329 GPS V2.0 which I bought in May. I believe at first it worked fine, but now I get weird behavior as follows: when turned on, it finds satellites as it should and gets a fix as it should, but when I start up the engines the trouble starts. I see that it still sees an unchanged number of satellites, but the position may either start to veer off radically or in some cases it just stops updating the position mid flight. Any GPS aided flight modes thus become unusable and unnecessarily scary to activate.
I have already done many things to stove off the possibility of EMI from different parts of the copter and a different GPS unit (older mediatek I believe) works perfectly fine.
Is there any record of similar cases? What could be the cause? A loose filtration capacitor or a bad solder somewhere else? Either it is triggered by vibration or the EM fields caused by the ESC:s and motors. It is difficult to see how it could be a firmware issue (although it could).