I got this:
ERROR 1213 (40001) at line 1: Deadlock found when trying to get lock; try restarting transaction (snapshot conflict)
But the problem is, the updates were no overlapping. I controlled all the updates and the "where x-y and z=t" conditions made it impossible to overlap a single row. Also the message mentions "snapshot conflict" and that makes me think this an internal issue with RockDB. That's why I am reporting it as a bug.