Lowrance 3500 works then blinks .5

[Bfrance1978]

I have a lowrance 3500 installed in my 2006 Tahoe q4. It will be working and appearing to be reading accurately, then all of a sudden it will start blinking .5. Any idea what is going on?

 

[NYBo]

Is this when moving? That would indicate a problem with the location of the transducer.