That could be possible. I had both a USB GPS
and the main Raymarine
GPS connected but I thought I had the data from the main GPS filtered out. I disconnected the USB one and OpenCPN was still getting GPS data. On my last trip there was random track points thousands of miles away.
I will do as you suggest and monitor
the source of the GPS data and also see if odd or spurious data is being generated
Thanks for the help.