Cubase 12 cannot run some C11 projects on Windows 10

C12 uses more resources than C11 on my system. I cannot run some C11 projects with existing plugins. I have mostly VST3 plug-ins. The UAD bundle is VST2. ASIO Guard meter much higher; it also overloads. Removing plugins seems not to really help, as much as it does in C11. There is a small burst of distortion when saving running projects. I used my entire previous preferences folder. Haven’t tried a reset as I’m in the middle of something.
AMD Ryzen 9 5900X 12-Core Processor 3.70 GHz; 32 Gb RAM. Windows 10.