Anova Sous Vide "Low Liquid" warning

I have the Anova One Sous Vide immersion unit. In theory and in marketing, you can just "set it and forget it". Compared to fiddling with stovetop dials and periodic temperature measurements, it is super easy.

However, the last time I used it, the unit would disable itself within a few minutes and throw a "low liquid" warning despite a liquid level near the max line. That really hurts the utility of this thing since I still have to babysit what I'm cooking or else the food could dip into unsafe temperature territory for hours without me knowing about it.

Halting the device because of low liquid is a good fail-safe on top of the other safeties e.g. fuse, temperature probe which would shut down the heating element anyway at high temperatures, metal casing ... but it should never activate if the liquid level isn't actually low.

What could it be?

At first I thought that maybe there was some debris in the unit blocking the water level sensor so I removed the metal housing and rinsed it with a produce sprayer. No luck. Then I used a Waterpik because there's one crimped part that could trap material. Still nothing. The manual says not to use de-ionized water so I added a pinch of salt to ensure conductivity. That fixed it for about an hour and I was pretty happy.

Then it failed again.

The water level probe looked corroded so I scrubbed it with a pipe brush but it still failed. Next step? Disassemble, continuity testing, voltmeter etc. Checked out the Anova forums for return information but one person in the Anova forums had luck with their malfunctioning unit by raising the unit off the pot bottom. Not sure why that would affect anything since I've used it plenty of times before but maybe there's some odd shorting issue. Placed it on a plastic cap in the pot and it ran again.

Then it failed again.

The forum had one guy with a generic Error message on one of the beta units find a solution through descaling.

So I soaked the unit in vinegar and ran it until it stopped. Had to do this a couple times but it seems to be working now. Lamb leg had since been cooking in the oven so it's not a real test but it ran for a good amount of time.

I don't think the descaling cleaned the sensor since I had scrubbed it and the unit still failed almost immediately.* What I think happened was that the scale build up caused the heating element to run too long and it overheated. I noticed some clicking noises prior to each failure so maybe the fuse needs to be replaced. It's probably not a failing fan since that runs fine.

Maybe the programming runs something like IF internal temperature > thermal limit THEN display "Low Liquid"

Although I plan on descaling the unit more frequently, the engineering could definitely use some work! Aquarium heaters work constantly and for orders of magnitude longer time than I've used this sous-vide machine. Electric kettles can be absolutely covered in scale and still perform. My Keurig gets used frequently and only requires descaling if the coffee output volume is noticeably lower than normal. But it still works. While the Anova immersion sous vide machine is a propeller, thermocouple, water level sensor, and heater all digitally controlled, it really is a simple design that ought to be more reliable. Maybe I got a lemon, given the large number of five star reviews on Amazon, but at the very least, descaling should be specified as necessary and routine maintenance.

* One of the Anova engineers states that discoloration on the water level sensor is normal. If it really is the case that the sensor malfunctions because of scaling issues, a bob type system would be better.