I’ve seen this before in the past and if I remember correctly it had something to do with RAM? Seeing you have 64 GB it’s certainly not insufficient memory? What could happen is if you let windows handle your swap file automatically it might create a massive 96 GB file. The chance of hard page faults increases significantly. As a result Cubase can’t match the project currently stored in memory with the one saved earlier to disk and offers the option to save it under another name. Especially with larger projects it’s more likely to happen.
If you have not manually adjusted your swap file settings you could try to turn it off completely but then you can’t produce system memory dumps anymore. If you still want that option you could set to 4096 MB or so, that is sufficient. But I have it disabled permanently because I next to never get BSOD’s. If you still get errors you might have to test your memory and see if it’s reliable. But lets hope it doesn’t have to come to that?