How are you exporting the files in DR (daVinci resolve?), Video or data? Quicktime has some very weird ways of automagically remapping ranges that can be quite infuriating, and invisible to the user.
As you noted, there’s a lot of options when you choose AE to manage the color space. Regardless, as long as there’s no clipping going on, you can spend a lot of time diagnosing the problem, when it’s a lot easier to adjust the gain and pedestal within AE to the right values.