Is this a transducer, or display head (ST60 Tri-Data) problem?

[sailjumanji]

Have a Raymarine ST60 Tri-data (depth, speed thru water, temperature), and a ST60+ wind, that get data to a NMEA2000 network via a Seatalk1 to Seatalkng converter. The depth is then repeated on my Zeus2, which is also on the network. Previously this all worked fine, and I could see the depth as well as all of the other ST60 data on the Zeus display.

Boat has been idle for a couple of months. Couple of weeks ago, went out for a sail, and when I removed the cover for the ST60 tri-data, noticed the screen has a dark area in the middle. Instrument seemed to be working fine though, and the depth was being repeated by the Zeus display (so not a big deal). We sailed for a while, and I noticed the ST60 display was occasionally losing the depth. When it does this, it flashes at the last depth recorded, until it reacquires depth. It’s done this when sailing offshore, and depth was over 400-600 ft - it's generally just losing the return signal. But here, water was only about 50 ft, so shouldn't be doing that. (It also did this, in 15 ft of water.) When that happens, the Zeus2 displays something like 140 million - which is obviously just a default for no depth.

At one point, when the ST60 had flashing depth, I turned off the instruments and turned them back on again. Thought maybe something would reset. When I did that, the ST60 came back with up with multiple bars for depth, and the Zeus2 just showed the same bars. Eventually the ST60 started displaying depth, and the Zeus2 repeated same.

Of course, now that I am back at the dock, the depth is working fine.

Raymarine doesn't make ST60 or ST60+ anymore, but the i50 is reportedly backwards compatible to Seatalk1 (as well as outputs Seatalkng). The issue is that I don't know if I have a transducer problem, or just a display problem. West Marine rep - who maybe knows his stuff - says that if transducer is working, and display not, the depth should still get onto the NEMA2000 network to be seen by Zeus. Another rep said different, that the ST60 display basically converted the signal to depth – so it could be the display problem.

I have not jumped into the water to check for barnacles on the transducer face, as I just cleaned the hull a couple of months ago, and the water is still pretty cool. (Rest just shows a thin layer of slime, that has never been issue before.)

So, anyone here have experience with this? Thoughts on whether the display is failing, or the transducer.