This slide from the briefing, translated using Google lens and posted on twitter, indicates that one of SLIM engine nozzles fell off during landing.
Yikes 😱
It shows an image of the falling nozzle captured by one of the cameras around 00:19:20 JST, just when it lost telemetry.
With one nozzle missing, the lander would have started rotating, while the software tried to compensate using the other thrusters.