Lithium batteries again?
Eyewitness reports said smoke was pouring out of the back of the airplane, so it sounds like it might be the LIPOs.
OTOH, the Lion Air crash analysis of the DFDR showed the pilots were struggling with the automatic safety system repeatedly pushed the plane's nose down.
Given the vertical speed chart shared for the Ethiopian Airlines 737, it may be the same cause as the Lion Air 737.
Apparently, the Lion Air jet had previous problems with it, but the pilots weren't informed, nor did they recognize what was happening or take the necessary steps to turn off the system.
From the Lion Air article:
Lemme described "a deadly game of tag" in which the plane pointed down, the pilots countered by manually aiming the nose higher, only for the sequence to repeat about five seconds later. That happened 26 times during the 11-minute flight, but pilots failed to recognize what was happening and follow the known procedure for countering incorrect activation of the automated safety system, Lemme told The Associated Press.
Lemme said he was also troubled that there weren't easy checks to see if sensor information was correct, that the crew of the fatal flight apparently wasn't warned that similar problems had occurred on previous flights, and that the Lion Air jet wasn't fully repaired after those flights.
"Had they fixed the airplane, we would not have had the accident," he said. "Every accident is a combination of events, so there is disappointment all around here," he said.