the plumbing for the livewells and all of the other power wires are all around it
Could it be that you have installed/moved wires around and are now getting some
type of electrical interference that wasn't there previously?
Have you put in a new engine or changed/added other electrical devices to the boat?
Have you rewired anything?
Have you had a big shifting of weight in your boat (front to back or side to side)?
it worked perfect for 9mo's and now doesn't..
If you installed it with an air bubble in it, I can't figure out
why it would work perfectly for 9 months. It would have NEVER
worked perfectly.
Everytime I have called HB CS I get flack from the obvious cheaply hire help that read from an instruction manual.
I'm sorry but this seemed funny to me. If a person doesn't have first hand knowledge of
your unit, they would have to refer to some kind of written document to try and
help you. I wouldn't be too hard on those customer service folks. They are genuinly
trying to help you.
The tranducer itself may have just gone bad. These things do happen.
I don't know if your unit is still under warrantly or not, but the problem is
you'll have to beat the h@ll out of the thing just to get it out.
If it wasn't already bad, I'd bet it would be bad after the beating.
Usually a hammer and electrical components don't go too well together.

If I was you, I'd try to eliminate any obvious problems first, with interference being at the
very top of the list.
If it were me and nothing else worked, I'd bite the bullet and purchase a new
transducer. Get some instructions and the right adhesive materials and read everything 5 times,
then install it once very correctly. I would take my time with the installation and do it right.
P.S. Before gluing it permanently to the floor of your boat, test it to make sure it works first.
Good luck.