If you embed a timeline at the very beginning of your main timeline, the first few seconds of audio won't play after you first load the project.
The only workaround seems to be to go into the embedded timeline, play the audio manually, then go back out to your main timeline and hit play again. Then it works.
This is super annoying because I'll often exit and restart Resolve right before I do a 4K render so it has a fresh start and has less chance of crashing.
Then of course I forget to do the workaround and after waiting 1/2hr to render, I have to start all over again because the first few seconds of audio are missing

Very strange one. System/version/etc. should all be in my sig.