Beyond that, the behavior is definitely not normal. We will need to simulate your account here and run some tests. I will see what we can do about it but please try the above suggestion first.

This is definitely unusual, Saillogger normally eliminates all those starting points automatically and works without any issues. You’re clearly observing something different.
Having a position all the time is actually a good thing, so that won’t cause the issue, but I suspect it has something to do with that USB GPS.

I presume you have a GPS source on your NMEA network (chartplotter, AIS, etc.) that comes online before you start moving. If so, can you configure a priority so that your USB GPS is always the lowest priority and only used when nothing else is available?

Go to Signal K → Server → Data Connections and, using the Priorities table at the bottom, configure priority for your navigation.position and give higher priority to NMEA sources (make sure your instruments are on while you do this). Put the USB GPS at the bottom, and set a timeout of 5 or 10 seconds.

It will look something like this:

Make sure you restart Signal K afterwards and let us know what happens on your next trip.