Resolve M1-made HEVC files won't play back in QT on M1

I have a project that I've moved from my MBP (Resolve 17.0 build 39) to a new Mac Mini M1 (Resolve 17.1 b10).

In Resolve, everything is fine with the project in the new computer. However, when I try to play back my rendered HEVC file in the Quicktime Player, or using the spacebar preview in Finder, I get the message "This file contains some media that isn’t compatible with QuickTime Player."

I *can* play back the file in VLC and Handbrake, and if I upload the HEVC output to our digital asset management system (or YouTube for that matter) they're accepted just fine and ingested as expected.

The HEVC file I created yesterday with the same timeline in 17.0 on the Intel machine playback fine on the M1 Mini. The Deliver settings were the same -- preset h.265 master, and change to an mp4 wrapper. Here's what finder makes of yesterday's vs today's file. My Google search hasn't found this is a widespread problem, but maybe this is a known issue?

Screenshot 2021-03-03 at 13.42.51.png (359.81 KiB) Viewed 675 times