396 goes off and on by itself while navigating.

[Peobody]

This discussion contains a picture of using a piece of self-stick foam weather stripping to create a more forward and secure cable end. I have used this method on both of my XT mounts.
viewtopic.php?t=2260&hilit=foam&start=10

[Wallace]

I had an intermittent power supply problem and it turned out to be a poor contact between the cradle pins and the Zumo.
I scrounged a piece of 0.6mm fishing line from a friend. Tied a slip knot around the power cable where the plug met with the cradle and I have never had that problem since.