The "someone is coughing in the background of the era change screen" got a ton of un-critical attention. I am 99.999% certain it is BS (vids inside) and it shows how willing this subreddit is to just dogpile on anything right now
See here (volume warning) - https://streamable.com/9xdmrf - The main menu loads behind the screen and you can briefly see one of the leaders load in, followed by a rustling noise, etc.
The same noise is heard here (again, volume) - https://streamable.com/30kqo9 on the main menu.
The reason why no one is able to pointpoint the exact noise is because the leader is random. Leader animations are still going in the background, and the sounds are still audible. This includes grunts from Charlemagne, etc. It's definitely janky but far less janky than what is being alleged.
There are so many busted and weird things going on with the game's polish that we don't need to be taking every suggestion someone makes uncritically with no evidence, upvoting it to the top of the sub, etc. "Oh but the fact that I believed it speaks to the nature of-" no, stop.