Have a 98 nitro lx with wide 128, humminbird has always worked well at any depth or speed. Even running 40 on slightly rough water it always displayed a constant picture on the screen. Here lately, unless I'm doing 15 on glass smooth water the image skips out. The diagnostic says its good, but it doesnt seem to keep up. I'm not sure if the hull mounted transducer or the depth gauge is going bad. Any ideas?