Thanks for your reply. I did set the background to black, and the loading layout page only has 2 text objects on it (to display "Loading..."
and to give the % (with>> round(loadingprogress*100)&"%"). That's very light weight, but it's still happening.
To make it more clear, I made the loader style to display the %, and now I can see that it loads over 75% before switching to my loading page.
I can PM you OneDrive link if you'd like to take a look.