Hello Greg,
It happens when I'm on the boat, I'm using a navionics gold chart card, I'm not recording/mapping any information when it happens. As I say it happens when I'm scrolling through the views.
I'm presently away at work at the moment but will check which version I am running when I get home, I downloaded the update around May time last year, it had the countour mode fix/option to get rid of the water column if required
Cheers