I have a PC with win 11. I had the same issue earlier after the change from win10 to win11. On my notbook I have win10 so a could play until today (yesterday evening there was no problem.)
As I know there is an issue on win11 so it is incompatible from the begining. Maybe there was some find of windows uppdate that occures the problem on win 10...
Do you have any information about the incompability on win10?

I have Win11, I have no problems until mid-late game which is normal since it's a 32 bit app.
Are you using a mod?
Perhaps you have app (s) running in the background that are using resources?
Next Time launch it with TM running and check to see what's going on if indeed it's a OS or app problem or neither.
I have dual monitors with TM on my other one, so I can always check to see how everything is going. My normal is 2% cpu and 30% memory.

The troubleshooting has to start somewhere.

I have a few comments, which may or may not help.
The mod is using way bigger maps than the game was originally designed for. This makes pathfinding more CPU intensive. Late game gigantic maps requires a high end CPU even by modern standards. It works with any CPU, but it might end up being kind of slow.

The game can run on anything from a GPU point of view, but it is a CPU heavy game. It's quite possible that the CPU will be hotter than you would normally experience during gaming. As such some computers, particularly laptops might thermal throttle.

As for it being a 32 bit application, then yeah that could be a problem if you run out of memory. After playing for a while the free memory might get fragmented and again the big maps can result in using more memory so if it's a problem, try a smaller map.

As for windows causing issues with new updates, while it is possible, it's not something, which has been confirmed. It's also possible that it could be a driver issue. I once lost all fan rpm sensors due to a motherboard driver update and got them all back with the following update. Updates are usually better, but once in a while they might not be and particularly old games will suffer from not being tested properly with new drivers.

I am running the standard game with no mods and even on the smallest map i still have the same issue. when i run task manager everything looks normal with no background apps running. Again every other game i own runs perfectly and i have a wide range of new and old games that are around the same in resource requirements and also much higher.