Yes, I am using Mac OS Big Sur, 11.2.3 (20D91), on my newest Mac desktop.
I have the same Teeth Settings issue on my older Mac desktop with this configuration:
iMac (Retina 5K, 27-inch, Late 2015)
macOS Catalina 10.15.5 (19F101)
3.3 GHz Quad-Core Intel Core i5
16 GB 1867 MHz DDR3
AMD Radeon R9 M395 2 GB
This older Mac has: Crazy Talk 8 standard for Mac OS X 10.9 and above 8.13.3620.1 I had the same issue with the previous version of Crazy Talk.
I do not want a refund. I will continue to use the product.I realize that your company does not issue updates, but someday there will be a version 9 so I hope that you will send this issue to your software engineers so that version 9 will not have this issue. Also, it would be helpful if they improved lip syncing. I do not import audio, I just type the text, so at the very least, they should be able to make lip syncing for typed text more accurate. Also, I hope they can find out why the 3D portion of the app keeps crashing (when importing a head-not when using a character that is included with the app).