A subtle detail was the failure of transducer #3.

A new one went in but still yielded a short period of low flow, then shut down & leaked lots of water.  There might be a bad screw hole leaking water.

The original transducers have lots of scale but flow like they were new.  Transducer #3 got a new driver board which didn't make any difference.  The leading theories are a bad cable or the transducers having to be matched to the driver boards.

A new enclosure was already conceived to move the transducers closer together.  To do this, they got a common cap which would have required removing 6 farsteners to access 1 transducer.  Obviously, it's not practical in a world where transducers are consumable & must be replaced 1 at a time.  The mane desires would now be thicker walls to try to reduce the water leaks, possibly more transducer spacing to keep water from landing back on the other transducers, possibly a 4th transducer.