The switches have protective guard rails on either side of then, and a safety cover that must be pulled upwards before they can be moved. They are designed to be hard to accidentally flip, because the consequences could be fatal.
The report says that they were moved to the off position, and back to on again in the space of 1 second. That's barely enough time to pull the cover up, move them, and move them back again, if you are doing it deliberately. The CVR has one pilot asking the other why he flipped those switches, to which the other replies that he didn't.
The protective covers could be faulty or missing. There was an FAA notice back in 2018 about some being installed without the covers. They might have been replaced with the wrong type during maintenance too. Even so, it seems like it would be hard to accidentally move them back and then forward again, given their position.
Two faulty switches seems unlikely too. An electrical fault is another possibility.