Interesting. I’ll try my best to recreate the problem but it does sound like something for the UE engineers. If you feel like going through the process, feel free to create a ticket on answerhub (https://answers.unrealengine.com/) and attach your DX Diag and any relevant logs and then message me with a link to the ticket so that I can assist. Several hours of loading is just crazy.
Thanks again for your feedback!