We have an Opty Mist, the Albany, since 2013.
In December 2020, I searched for help with it, and found this site and thread. Wow!
Having had the (what now seems like typical) problems, I thought I'd say what I have found:
The heater always works fine (although not often used), so no issues.
The LED log effect always works fine, no issues.
The uplights work ok, now that I have replaced many of the lamps, and replaced all of the lamp holders. (They get really hot, so needed to replace the holders, and used the ceramic type).
At some point, the magnetic switch stopped working, meaning that the water level in the sump wasn't detected, and the lamps and mist maker would never try to run. I changed this switch, with one bought from CPC, and then that part was ok.
The little fan stopped at some point, and I discovered that this wasn't getting any power. I derived a DC supply from the AC supply for the lamps, along with a speed adjuster, and that all seems fine now.
The big issue, was the mist effect.
This worked great for the first few years, but then started to get progressively less consistent. Often wouldn't start properly, and then eventually even after an hour, would hardly do anything.
We worked out that the sump would sometimes overfill, and that played havoc too. This was due to a tiny hole in the blue water tank, which I smothered in airfix glue to seal up. (Air was getting into the tank, so letting water out when the sump was already full).
After trying all the tips with the must issue, (clean the disk, descale) our conclusion was that we needed to replace the transducer assembly. We bought it (very easily) from Mouser electronics.
The mist maker, is a TDK module (circuit board and transducer).
I googled NB-80E-01-H, and the Mouser catalogue number came up from there.
It turned into a really easy fix, just taking out the old transducer and its control board from under the base of the sump, and fitting the new on in. I put a dab of silicone grease on the rubber o ring when fitting it back together, to reduce the chance of water passing by it.
This was done on Cristmas eve 2020, and used everyday since, and each time has been fine.
One of those fixes where you think - should have done that ages ago!!! We live and learn.
Hope this helps someone with similar issues.