Mike Spera wrote:
In my previous posts, I described what appeared to be random signal lock
losses with my new 396...

You have three solutions:

1. Get rid of the 12D

2. wire the "keep-alive" pin on the 12D direct to the fused always-on
"clock" circuit in your airplane. (see #3, below)

3. Always program a non-offending frequency into your NAV receiver
immediately after turning on the avionics master. (By default, the 12D
defaults to 115.5MHz if the keep-alive is not connected. This is ONE of
the Nav frequencies that clobbers the GPS)