Hi welcome to DUC.
Unfortunately a huge amount of the expected info is missing. Start at “Help us help you” up the top of each DUC web page.
Your Profile shows 2020.9.1 and 8GB of RAM (below the minimum system requirement BTW).
What exact Windows versions?
What IO buffer size and sample rate are you trying to run at?
What interface and driver version?
Sandra report?
What changed on the system? Something had to. Windows update running? Added new hardware or updated a driver (for anything?). When did you upgrade to 2020.9.1 and was it running OK before that?
Is the PC fully optimized? Every last thing done? BIOS settings? Bluetooth and WiFi off... do every last thing for now.
CPU errors at low % CPU usage happen all the time. That gives no useful info. Stop looking a CPU meters.
You did a full clean Windows install onto a clean partition or effectively erased the previous partition? So are sure every last old plugin is gone? If not move all .aaxplugin files out of the plugin directory and trash prefs.
In addition to fully optimizing the system you should try setting processor affinity, see
http://duc.avid.com/showthread.php?t=410535&page=2