Originally Posted by
Speed of Sound
there is no evidence for it.
I kept hearing that that too on MAX thread, when people suggested the stabilizer trim thumb switches might not work under some circumstances.
Although there has been circumstantial evidence that it may have happened on the accident flights, other people were very vocal contesting that claim, along the lines of: "there is no evidence that those switches can fail to work properly, the MAX issues have been under thorough investigation for months, if there was anything to suggest that those switches could fail to work we would have heard about it by now".
Ironically, just a couple of days after those claims of "lack of evidence", evidence came out that it may have indeed been possible, since such a condition was discovered in a simulator test performed by FAA pilots.
Reality seems to have a particular habit of soon proving wrong people that claim large amounts of smoke is not evidence of a fire. And there has been a lot of smoke in the last decade about Boeing trying to deliver aircraft as fast as possible, and disregarding quality issues because of that. Now that there is concrete evidence about a bit of fire, it's not unreasonable to assume that most of the smoke may have been caused by fire as well.