I think that should be 2022, that's when the polarity fix became standard, but that's a good point. Space Heater was discontinued a while ago so there are probably more Space Heaters out there without the fix than with it.If the space heater was made before around October 2023, it may have been made before the polarity correction was standard, which can also be a cause of unwanted noise
@ContraToronto if you can post or PM me a picture of the circuit board I can tell you if it has the polarity issue that caused issues in some cases.

