We have access to 3990X machines, so if you send us your problematic scene, we can test it. If it's also slow, that could mean that there is some problem specifically in this scene. If not, then it's most likely something with your system (could be an older plugin version or similar, we could try a remote session and see if we find the culprit).
You can submit a new support ticket and attach very large files here. Please archive the scene with all assets (File > Archive option in Max):
https://support.chaos.com/hc/en-us/requests/new
