I only just started to see this, in the past my GPS has worked flawlessly every time in the same area. It occurs almost every time. The GPS will lock in with a very tight circle but will be 1000ft from the actual position. This makes navigation almost useless, as it thinks I am an entire block over (or not as seriously 1000 feet farther or back).
The offset seems to be directly West. This is in the South Bay area.
More specifically the circle will be larger (50ft) and is close to correct, but then the circle goes smaller (10 ft) and moves 1000ft to the west, which is incorrect.