Alright, I tested it out on the old machine. For the record the Old windows 10 machine runs on a Intel Core i5 - 4570 @3.2GHz.
It was also a machine that happened to play the last 4.0 version of the game. But when I ran the game, the bug did not happen, It was unreproducible on that operating system.
As for my windows 11 machine, it runs using an AMD Ryzen 7 7800X3D CPU. So, it might have something to do with windows 11 specifically.
One idea I could recommend and try, but I'm not sure if you can do this, is try running the game on a virtual machine of windows 11? I don't have any virtual machines set up sadly so I can't help testing there but, that might aid to see if its specifically a windows 11 issue.
Seeing that this chain is getting long however...is there some other form of communication I can use to contact you?