This is a weird one, I think. When I use the drop down in Project Settings > Maps & Modes > Game Default Map and try to select my MainMenu level, the selected map does not change. Instead, it just stays as whatever the previous value was (whether it was another level or none). Changing between other levels works just fine. It is only my MainMenu level that does not work.
I tried Googling the issue, but it is hard to get Google to understand what my problem actually is, so instead I just get a bunch of articles and forum posts about how to change the default map in general versus what is happening to me.
Has anyone seen this issue and/or know what I can try to resolve it?