No GPS signal on startup

I fly a 2009 Vans RV10 equipped with dual Advanced Flight Systems 5600 EFIS, a Dynon AP (not Dyson per spellcheck), and an Avidyne 440 GPS/Nav/Com.  I do not know when the GPS was installed.

For several weeks now I am experiencing difficulty with "GPS integrity" on my EFIS screens, and a red X and no GPS signal or similar message on my Avidyne unit.  IFD Software version is 10.2.2.0.

IF I stay on the ground long enough the message goes away.  Forced reboots don't seem to help.  If I take off the GPS starts working during the flight.

My AFS/Dynon stuff has a VFR GPS, a dynon 250 I think.  This always has satellites when I check.

I've read that these symptoms are what can happen when an internal battery in the unit goes bad as the unit has to look for satellites afresh, with a good battery these things are remembered at start up.

The GPS does not fail in flight.

In this first video you see the message, GNAV 1 is the Avidyne unit.https://www.youtube.com/watch?v=kyzYHqmV6cU

In this 2nd video we can see where the Dynon GPS has signals at start up and the Avidyne does not.  https://youtu.be/hlr6AoMT2pQ?si=2TuHz9U_9OPZFKjF

So, is the internal battery causing my problems?  If so, how do I get it replaced, how much does it cost?  Is a loaner unit available?  How long does this take?

If this is not likely my problem, how do I troubleshoot this further?

Again, thank you.