Star Schema gives "Exceeded Resources" Error whereas Flat Table doesn't?

Have you tried getting rid of everything with flat? Its likely getting confused. You should always try using star schema concepts, plus it looks like you don’t have the EDNA Date table. (which you should have)
Here is the link to creating the date table within the forum that @Melissa created: Extended Date Table (Power Query M function) - Power Query / M Code Showcase - Enterprise DNA Forum

Thanks
Keith