A few moments of confusion followed before we realised that he must have entered the coordinates as degrees E instead of W and was 60 miles off course.
But this was a human error, not a GPS error. Hopefully the glider pilot learned about "gross error" checks from that episode. Rubbish in = rubbish out.
If anyone glibly follows a GPS (or any other form of aviation calculation) without checking that the plan looks perfectly sensible, then it's not at all surprising if he/she gets lost at some time.