Is it possible there is a bug with legacy (0.15x) flow scheduling as of last night? Despite not making any changes yesterday, we saw jobs start piling up late in the evening (UTC), where previously everything had been running fine for many months. I know the deadline for switching over to 2.x is fast approaching, and we are underway now with our migration, but as i say we didn't touch anything at all yesterday so fairly sure this isn't something on our side.

Happened to me too. I just reactivated the schedules from the web UI and it started working again