Product review (5 stars): Interesting take on the repair.
Like many others, I've had this humidifier for abut 5 years, and it is a high maintenance device.  But it does work well.  Yes, next year I'll have to deal with aging cracking plastic covers and tanks, but this time my problem was the same old "overfill" error problem I've had in the past.  Three times previous replacing the level sensor alone fixed the problem, but this time not at first.

Lots of head scratching till I examined the unit in the dark with a flashlight just after a reset-restart.  To my surprise there were "vents of steam" rising from around the temperature probe, as well as near the side catches on the aging tank.  This time I replaced the gaskets under the temp sensor and snugged things down with the torks screw to where I saw no steam, and left the top cover off.  Reset, and everything has been working fine since.

My conclusion was that the accumulated steam inside the control area was affecting the sensor plug and circuitry causing it to show the overfill fault.  Has been working fine for three days now.  Have my fingers crossed.  Not sure how much a new tank (which hopefully will have its own new gasket) and cover will cost, but that's next year.

Regards