Most of the issues can be solved if the repository contains scripts and information on you to onboard a person or a new development environment. I used to work somewhere where all you describe took at least 1m onboarding. With scripting that helped drive our CI and CD pipelines, this process was reduced to 1d.
The biggest gap is in my opinion the historical context.This is something that even when a proper wiki is used it is difficult to understand especially when people have move out.
The most annoying is the acronyms and lingo. This also depends on quality of collaboration and culture. Some cultures think that converting all verbal and written communication to acronym based it helps accelerate the discussion where instead it only creates more confusion and less quality thus reducing the speed at the end. It also makes some people feel important. Lingo will always happen but when new people are in the discussion it should be limited. Usually when there is no change it means two things:
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