At the risk of being even more boring, for which I apologise in advance...
I didn't say it was map shift. Map shift and GPS failure or degradation are two different things - both with potential to do harm to the navigator (air, land, or sea).
My first post here clearly differentiated between map shift and GPS problems.
'You fly the missed'... Tracking, just, what, to your next destination?
GPS approaches may work remarkably well, when the GPS works remarkably well (not all the time in my very limited experience). So do NDB approaches, VOR approaches, and ILS approaches, not to mention SRA and PAR, TACAN, and QGH (what fun!).
By the way, 'losing RAIM' and having a GPS failure are not the same thing...