Ultrasonic Cleaner Very Weak Cavitation - What causes this

I have a 2 qt Sonix IV Ultrasonic Cleaner that has a very weak
cavitation. I tried the aluminum foil test and it only produced one
perforation in a 10 minute span. I also observed that it only raised
the water temp about 8 degrees with the heater off.

What's the most likely scenario? I would assume the semiconducters
are OK since it does produce some cavitation? Do transducers
gradually weaken over time? Could a leaky cap. distrub the
oscillation reducing the units performance?

If it was DOA the diagnosis would be easier but what causes these
units to weaken?

Thanks
.