The current amount of bugs introduced with the patch shows how bad the development workflow is. There doesn’t seem to be any sort of automated tests. Because those would have found 95% of the bugs instantly. Without a proper development foundation the game will die.
If Relic isn’t able to do this on their own, Microsoft should spend some of the cash to get consulting on how to implement it. Best known for their automated tests in videogames are the Factorio devs. Here is a video of their testing pipeline running tests after each pull request (code change):
Their game is way more complex than AOE IV and they are able to release huge updates with very little and minor bugs only.