Lossy audio even at PCM24

Hey, I'm having an issue with rending lossless audio in a .mov H.264 container. I'm running 17.1 on a M1 MacBook Air. Made a 4824 WAV mix of a multi-channel classical recording in Reaper and ported over to DaVinci for video editing, but the sound quality is definitely diminished on playback in DaVinci. I figured this was a monitoring issue, but even when I set the audio output to Linear PCM 24-bit when rendering a H.264 Master, the audio in finished video sounds a bit hollowed out, as if the original audio file was downsampled or converted into an MP3 somewhere upstream. I did a null test with the original audio in Reaper and the audio is definitely being processed somewhere in DaVinci. Conversely, when I render a H.264 .mov in Reaper with embedded audio set to linear PCM-24, the audio output is perfectly lossless, and a quick null test proves this.

Is there a preset I've missed in the project settings, or something on the delivery page?

Thanks!

Have you checked that the render from Resolve is actually in the correct format with something like MediaInfo?

Maybe it's not outputting what you're asking it to.