66i Struggles in GPS+GALILEO Mode

[baldamberg]

My GPSMAP 66i performs worse with GPS + GALILEO enabled.
The device has a hard time finding a signal (EPO is current).
Most of the time it keeps cycling between 366m, 3m and "signal lost".
Even when it manages to stay at 3m with good satellite signal for a couple of minutes it spontaneously decides to forget all the satellites and start searching again at 366m accuracy.
This results in unusable tracks when I am hiking or mountaineering, because this issue gets worse when moving.
I own a Fenix6X (GPS+GALILEO mode enabled) as well and it records proper tracks in the same terrain that my 66i struggles in with GPS + GALILEO.

However, if I only use GPS my 66i works as expected without any noticeable issues.

Has anyone else encountered similar problems?

[GPSrChive]

Please provide the Device Software Version and GPS Software Version as reported in the Setup > About page.

[baldamberg]

Device Software Version: 9.80
GPS Software Version: 2.90

I bought the device in 2020 and this problem has existed with earlier software versions as well.
But I just discovered this forum recently.

[GPSrChive]

We are testing our 66i v9.80/2.90 now, will report back later....

{later}

After several hours of testing, no drop outs from our GPSMAP 66i using GPS+Galileo. Accuracy always reported ~8ft once initially settled (no valid EPO). We did notice the GPSMAP 66i only found 5 of 8 available satellites, while the GPSMAP 67i found all eight.

What country are you in?

[baldamberg]

I am located in Austria in Central Europe.
When my 66i manages to stay at 3m accuracy for a couple of minutes it reports fewer GALILEO satellites than my gpsmap 67 as well (multi-band disabled).

Unfortunately Garmin Support was very unhelpful when I contacted them a couple of years ago.

I once met 2 people at a mountaineering course who both owned a 66i.
One of them had similar issues the other one did not.

[GPSrChive]

Could possibly be hardware related. Some models of Garmin GPSr will report the device hardware version in a diagnostic page, but I am unable to find this information listed on our GPSMAP 66i. Would be interesting to see if those with the issue had the same hardware version, and those without the issue had another hardware version.