G3X HSI keeps switching source to VLOC2

[PT20J]

I have a G3X Touch, GTN 650Xi (Nav 1) and a GNC 255 (Nav 2). I always use the G3X with the GTN (GPS1). But sometimes the G3X powers up with VLOC2 selected. Has anyone \else seen this and has anyone found a way to make the G3X remember the last used nav source?

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[Ulysse]

Yes, seing this regularly (g3x, gtn750xi, gnc255) but do not know why. I have just made it part of my check list

[Unit74]

What would trigger it to switch automatically? Inquiring minds want to know!

[Cruiser]

no GPS signal

[PT20J]

I received the following response from Garmin support:

Unfortunately, we don’t know of a way to control that. I was not able to get an answer from the engineering department as to why it is designed that way.

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[201Mooniac]

I'm guessing the power supply in the number 2 radio just has a larger capacitor which keeps the radio alive longer on shutdown than the number 1 and the G3X switches when it loses a valid signal from number 1.  You might want to try shutting down number 2 first on shutdown for a few times to see if that stops the switching.

[PT20J]

I did some experimenting today. Per the STC, the G3X is powered directly off the master switch and the GTN (GPS/VLOC 1) and GNC (VLOC2) are powered from the avionics switch. 

I landed with the G3X nav source selected to GPS1. I turned off the avionics switch killing the radios. G3X still shows GPS1. I turned off the master shutting down the G3X. I refueled the airplane and turned on the master but not the avionics switch. The G3X boots up with VLOC2 selected. 

EDIT: I should point out once again that this seems random. The last few times I did this it stayed on GPS1. 

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