In the "Order 66" arc of Star Wars: The Clone Wars, Tup's inhibitor chip malfunctions, causing him to begin executing Order 66 prematurely and murder a Jedi General. The malfunctioning chip is extracted and shown to be badly decayed, but no explanation is provided for what caused this to happen. At the end of the arc, Palpatine claims that a rare waterborne parasite was responsible, but he also claims that Fives was infected with the same parasite even though Fives' chip, when extracted, was perfectly intact, so he's almost certainly lying.
Is there any canon indication of what did cause Tup's inhibitor chip to malfunction? Or is it intended to be a riddle for the ages?