Although I'm a big fan of properly-used GPS (but not 'moving map' GPS as that encourages too much 'head in' time), I've noticed the odd glitch in the VFR-only GPS equipment in my 4 PA28s and also the occasional GPS wibble in the Y-code GPS element of the embedded GPS and laser INS in my 'day job' aeroplane. Which is why GPS-only is never used for navigation, GPS blended with LINS or GPS blended with a secondary INS through the Flight Management System is used for LNAV autopilot steering.
Nothing to do with 'not made here' - everything to do with safety of air navigation!