This reads very human but "that only demonstrates plausibility, not truth." reads AI ;) Are you imitating ChatGPT? :-) But I agree. This could be a routing issue or some other interaction. Could also just be overload of traffic between these networks of different capabilities. At you say, probably not rate limited in the interface between the systems.

It's not hard to screw up networks. I remember our IT person introducing a loop into a simple office network that took like two hours to troubleshoot.

You'd think they would have a) noticed sooner b) made the connection between the last change and the issues. But easy to be a backseat quarterback as they say.