[TG] [TG11] ST 40 Bidata depth failure

[Olmate]

My 5 yr old ST40 display started becoming unreliable a few years ago and would read 0.5 or 0.6, often scrolling back to that from whatever true depth and then would start working again after an indeterminate time.
The failures have become more frequent until now it seems permanent.
Cleaning the Airmar through hull transducer on my trailer sailer seemed to help once but not again so I don't think paint or anything on it is the cause. It's had several varieties of anti foul and no antifoul with no direct correlation.
Does that sound indicative of anything to point at the transducer or display?
Surely mine isn't the only one to have ever done this.