I have some anamorphic ARRI footage (2880x2160) that is not exporting correctly. The footage is interpreted correctly on input into resolve (reads as Cinemascope in Clip Attributes), but after applying a lut and exporting, the DPX output doesn't seem to be flagged correctly as anamorphic. Importing the DPX into Flame, Nuke and AE they are all reading it as square pixel. They all read the original ARRI footage correctly but not the DPX.
The output settings are Render at source resolution, Pixel aspect ratio is set to Cinemascope, and Force debayer resolution to highest quality is checked. I've also experimented with Disable edit and input sizing and Force sizing to highest quality on and off. Neither has any effect. In fact changing the Pixel aspect ratio from Cinemascope to Square doesn't have any effect either.
What if you manually set the sizing in Resolve as the clip is rendered? This has always worked for me. If the output resolution is 2880x2160 (1.33:1) that's how it's going to wind up. If you want it scope, resize it to 2880x1205 with a vertical unsqueeze and then it'll be 2.39. I would do a test and see if this will work.