vex problem??

[rap]

last year i noticed that if i had my lure just hanging below my vex it would show up then dissapear over and over again and it was sitting still the whole time. i also noticed when a fish would be beneath it, it would also suddenly dissapear then reappear while i knew the fish was just sitting in the same spot the whole time. now i did the air test on a hard floor that the vex newsletter explains... at the 9 ft mark, there is a green line, but it does the same thing, keeps disappearing then reappearing!! has anyone else experienced this problem before... i'm just trying to figure out if i should send the unit in to the vex repair shop or buy a new transducer??? it's very frustrating out on the ice when when your trying to entice a fish to bite then the lure and the fish keep disappearing and reappearing! thanks for any help