Hi Jim,
I duplicated the two adjustments you used and uploaded to YouTube and it played without any flicker. Here's what I'd suggest:
1. Start with a new project.
2. Upload the video.
3. Add the haze adjustment only. (Do not add the highlight & shadow adjustment nor the animated "Come feed the turtles".)
4. Save and export.
5. Test. If no flicker, add the highlight & shadow adjustment, save and export again.
6. Test. If no flicker, then add the animated "Come feed the turtles".
If at any point you get the flicker, the last adjustment is the culprit. Try changing the order of the adjustments.(e.g. First add the highlight & shadow and then the haze adjustment.)