So, in my case, the crashes happened because I hadn’t removed the logic of some plugins from 5.3.2 that hadn’t yet been released for 5.4.1. Also, on top of that, I discovered that my GameInstance was a child GameInstance object of a third-party plugin. Thus, if I disconnected the third-party plugin - my GameInstance stopped working, and with it all other Blueprints, most likely because GameInstance loaded a lot of important information, because through GameInstance I have implemented a system of saves. This was the reason for me in this particular situation.
As a result, I decided to give up the idea of porting the project to 5.4.1, I will wait for the release of updates for plugins and possibly hotfix 5.4.2, because now there are a lot of critical problems with optimization and engine crashes.