For anyone running into these issues: I recently wrote a tutorial that may help by giving a high level view of bp loading engine code and how it should work and then some tips on how to find where things go wrong. One of the first things to check being circular dependencies like rantrod mentions.
Don’t expect to solve all issues with it but it should help with understanding the engine code and narrowing down what happens in a project. If you have a repeatable problem (a working asset and repro steps to break it) that’s also incredibly useful, so please consider sending it with a bug report. Seeing the asset break or knowing exactly which class and subobject hierarchy is causing problems helps us eliminate more and more causes of this issue.