I'm having the same problem with mine, when I first installed mine I had it set about a half inch above the bottom of the boat. Recently I lowered it about a quarter inch below the bottom and I started getting the same images in the water column on the left side.
I'm thinking it's got something to do with the water turbulence from the strake on the bottom of the boat. Planning on raising it back to the original position when I get back home to verify that.
if you figure it out before I do let me know please