GNS530 NAV mode won't engage + workaround

[glideslope]

Hi,

Bump into this issue twice so far so I'm sharing my finding and analysis of the issue.
The symptom is that the AP will work fine, HDG mode will engage but not the NAV mode.
So what worked for me eventually was toggling the "1 2" and the "NAV" source buttons in the EHSI . I believe that it was probably enough to toggle the "1 2" but haven't reproduced the issue again yet to confirm.

My reasoning for the problem lies with another bug related to aircraft persistence. Sometimes it will load up in the GTN 750 configuration ( especially when loading on runway). I think that this messes up with the GPS assigned to the AP or something related....
my 2 cents...