One or more of the satelites was out of position for a while.
US DoD satelites do not go 'out of position'.
Turn off unexpectedly perhaps, but not go on a walk about.
Now, down to brass tacks.
I have personally used IFR approved (enroute/terminal/approach) GPS units for the last ten years, both in my private aeroplane and in heavy transport jets.
Only three times have suitable signals been interruped, and then only for a very brief time.
Once over Mt Wilson, Californa, where television and FM transmitters/antennas are located.
A total of twenty five.
Two times during intensional GPS specific area signal interruptions, as published by NOTAM.
GPS...made in America, and it works
good