AUHostingCompatibilityService Causing Issues With Audio Plug-ins

For reference, I'm on Big Sur 11.0.1 and Final Cut Pro X 10.5. And yes, I shouldn't be using my machine with so many plugins on the latest software but I had tested all of this on my MacBook Pro 13" for a month or so prior and it was fine (still is fine, slight spoiler for the rest of this meandering post).

Hello, folks! I have a really strange issue and although I've contacted the company that supports the plug-ins in question, I'm doubtful they will be able to help as I've updated both Final Cut and macOS to versions they do not support.

Basically, when I try to adjust any of the parameters with Izotope's RX4, RX5, RX6, RX7, or Final Mix plug-ins, Final Cut will either crash out completely or give me the following error:

And then all the audio plug-ins show yellow exclamations, even ones I wasn't trying to adjust, and are no longer accessible until I restart:

This was all working fine until I Force Quit Apple’s new “AUHostingCompatibilityService” that appears in the Activity Monitor once one of my audio plug-ins is used. I Force Quit it because at one point, it was holding nearly 150% of my total RAM hostage and paging out to my SSD. Ever since then, I’ve had this issue. Even stranger - my MacBook Pro 13" 2020, which I mainly use as a test machine, is working fine with these exact same plug-ins. 

FWIW, I’ve tried just about everything I can think ofL

I restored my machine to a Time Machine backup that I believe was BEFORE I had Force Quit that new AU service, which required a full wipe and reinstall of macOS and yet, there was no change in behavior. 

In addition, I uninstalled Final Cut Pro X, including all preferences etc, and the issue remained. I also tried to get the program to refresh or detect all Audio Units and no change.

Finally, I tried to uninstall and reinstall the RX plugins but this did not make a difference (truthfully, I only got as far as uninstalling all of them and reinstalling versions 6 and 7. Strangely, other plug-ins by Izotope, such as Neutron 2, are working fine. And my audio plug-ins from Crumblepop are fine as well.

Does anyone have experience with this AUHostingCompatibilityService? I just started noticing it after installing Big Sur. Is there a way to reset it or anything? I am an idiot when it comes to this lol

Note: It’s possible this issue was present before and I just didn’t attempt to adjust a plugin’s settings, but that doesn’t explain why it’s working fine on my other computer.  I’ve been using my Mac Pro with these plugins all week and had not experienced any issues until after I Force Quit the AUHostingCompatibilityService.