Windows Version 20H2, Build 19042.685, Pro, 64

This one is odd. Built a new PC in May 2020 using i9-9900KF and Asus Z-390E Gaming MB. I installed an LG WH14NS40
Blu-ray/DVD reader/writer from an earlier build plus a Creative SB X-Fi Titanium soundcard, also from an earlier build. Everything was fine until about 2 weeks ago when I noticed scratchy sound on some YouTube videos and also on a few Blu-Ray discs. Removed the X-Fi soundcard , reverted to onboard audio and downloaded latest Realtek drivers from their website. All was ok for about a week and noise started again. Disabled on-board audio in bios and installed a Creative USB G6 USB amp/dac external soundcard;crackling sound still there. The affected Blu-ray discs play fine on another laptop and home-theater Blu-ray player so it's not the discs. The affected YouTube videos play fine on a laptop. It's got to be a driver issue or conflict of some kind. I hooked up an Asus external USB Blu-ray player to rule out a problem with the internal LG. It too played the Blu-rays with a crackling sound. I ran SFC and it fixed a couple of errors, but not the sound problem. I do have an Nvidia RTX 2800Ti installed and Nvidia installs it's own HD audio drivers, but I never use them. The video card driver is up to date. All Windows updates have been applied. I tried a system restore as far back as I could (January 15th), but it didn't solve the problem.

As a last resort I can try re-installing Windows 10, but I wanted to see if anyone had any ideas first or something I might have overlooked. I'm hoping it's not something defective on the MB itself.