Thanks for the response Windell.
The GPS module has a red LED that flashes @ a 2 second rate when acquiring and at a 12 second rate when locked. It is always locked. I have about 25 GPS receivers in my home (some using the exact same GPS module) and none of them ever drop out. They are associated with my 25 Nixie clocks. So I don’t believe its a GPS signal strength issue.
What is strange is the drift rate is much higher with the GPS then the basic clock. Would it make sense even if I was losing lock with the GPS that the drift rate would be higher?
I suppose it would be a function of how the code is implemented…