Oh, just realized you said 40 minutes. I looked back in the monitoring data since January 1st for monitoring data with a 30 to 50 minutes offset and I see one server from France on January 21st that had a 31 minute offset (obviously it was promptly removed from the pool after that until it had better time). An IPv6 in the UK has a single measurement with a 47 minute offset on January 18th.
For what it’s worth, it looks like in the ~21 million checks done in 2019 there was just one server that had two measurements like that, so this year is on track to be many times worse.
40 minutes is weird though, and as others said a careful NTP implementation would ignore that.