If the GPS isn't used for awhile (like parked in garage not getting sat signals for several weeks) it takes a while to upload sat almanac data, to determine where the sats are and to lock on to their signal. This obviously not the case since it worked fine the first half of trip. Guessing if it persists, you may have a faulty antenna for GPS signals. Any chance you were driving in a gorge/ravine/valley, or somewhere geographical features would block view of satellites? Heavy canopies of trees and geography could block sat signals if the sats you were locked onto were low on the horizon.
Also, solar flares or solar storms periodically create atmospheric disturbances that interfere with sat signals, causing the positional error you experienced.
Also, solar flares or solar storms periodically create atmospheric disturbances that interfere with sat signals, causing the positional error you experienced.
