Denon x1400h, Apple TV, 65r625 Audio Sync
Received my TCL 65r625 on the 20th of November after my two year old smashed his toy car into our 65r615 (2018 model) and cracked the screen significantly. My AV set up consists of a TCL 65r625 (running Roku 9.2), a Denon X1400h (May 2019 firmware), and an Apple TV 4K (13.2). Right now I have my Apple TV connected to my Denon via HDMI and then my Denon connected to the TCL via HDMI ARC (HDMI 4 on the TCL). On the old panel, I never experienced any audio sync issues across any framerate or color space content on the Apple TV and I didn't really notice anything for the first two weeks until this past Saturday (11/30/19). First it was on watching THE REPORT (HD) on Amazon Prime and the audio was almost a second behind. I assumed it was a bandwidth or Amazon app issues and moved on. Then I tried watching THE IRISHMAN (DV, 24 FPS) and I noticed an audio delay as well.
Now it seems like every framerate and color space has a varying degree of audio delay. I've been troubleshooting for several hours and still haven't isolated the issue.
On my Denon X1400h, I've turned on and off Auto Audio Lip Sync and it seems to be worse with it off, but still not perfect. I can adjust the millisecond delay manually on the receiver, but it's so annoying because each piece of content has a different delay. I've changed the HDMI output from Enhanced to Standard (side note: on the 2018 version, this would disable Dolby Vision from the Apple TV, but now it doesn't on the 2019 panel). I turned off all the ARC features on the receiver.
On the Apple TV, I've tried to force different color spaces and different frame rates. I've done match frame rates and color spaces. I've calibrated the audio sync with the new Wireless Audio Sync feature on tvOS 13.2 on every frame frame, color space, and chroma. I did the calibration when the receiver's auto lip sync is on and off. I've done the calibration with the ARC on and off between the panel and the receiver. I've the calibration with the HDMI output set to Enhanced and Standard on the receiver.
I watched THE IRISHMAN on the TCL's native ROKU app and the sync was fine, but I noticed that the sound dropped after about 5 seconds. I have no idea what that's about.
I'm at a total lost.