C++ Classes / Components disappearing in blueprints whenever I restart

Try modifying the LoadingPhase of your plugin (in its .uplugin file) to something that happens sooner. See ELoadingPhase::Type | Unreal Engine 5.5 Documentation | Epic Developer Community for available loading phases.

If that doesn’t help, could you scour the output/message logs for any warnings/errors that get outputted after you start up the editor and open one of the blueprints with errors, and paste them here?