Well that's a first for me: an NTP Pool server sent a wildly wrong time, and systemd-timesyncd jumped the system time on Trastevere first forward 0.82s and then *backwards* 0.76s.
Thankfully Sunlight failed safe, crashed (which fired alerts), and recovered once the clock caught up.
WTF?
https://www.ntppool.org/scores/2603:c020:8017:3e00::123