Yes this is a real bug on xbox. I suspect it’s affecting a lot of people who are mostly not noticing. I think it has been happening to me for some time before I really cottoned on to the symptoms. The whole sim slows down together, even the clock. But it can also speed back up again. I suggest everyone on xbox to keep an eye on the rate of ticking off the clock and add their feedback to this bug:
This is not caused by intentionally changing simrate, and in my experience can slow down the sim anything from a few% up to 50%.