Sounds like tuesday to me. One thing you learn about exchanges (I mean all of them as a software category) is that you can’t trust: documentation, reasonable expectations, the experience you’ve got last week, the idea that all symbols behave similarly, reproducibility on test servers and vice versa, to name a few. Don’t rely on these and you’ll be relatively safe.

But really, expecting a deterministic confirmation is a rookie mistake. Exchanges feel very asynchronous after a short while and the intuition should tell you that that a confirmation is just “ok, I hear ya”, not “effective immediately we’ll suspend our queues and reschedule trades to fulfill your urgent request”. The temporal uncertainty of order status is a quite common phenomenon, ime.