A friend of worked at a company that sold CNC cutting tools and they had an issue at a customer site that they couldn’t replicate back at the factory. It turned out that the customer’s internet connection was so slow that the CNC machine would boot up, the customer would actually start cutting with it, and only then would the NTP daemon synchronize the time. This caused all sorts of failsafes and sanity checks to trigger and shut down the machine (which tracked its own velocity by looking at its position sensors and the system time) but when the machine was shipped back to the factory it would work just fine because it had a much faster internet connection.

recently had to do some socket level ICMP and UDP timing stuff and this article was a great little rabbit hole!