Asset Tracker Electron erroneous longitiude

Sometimes, the longitude from the GPS device is garbage for a very short while.
The Asset Tracker (v002) is stationary, on my desk. There are 2 other Asset Trackers a few feet away.
All 3 Asset Trackers have this malfunction.
Electron FW 0.4.8

Last good t.readLatLon() before malfunction:

10 seconds later,
37.663883,121.00001 <<<<<<<<<<<<<<<< BAD LONGITUDE.

10 seconds later: