I believe I know the reason.
My game started to have sound and lag problems when an allied lord tried to attack a lord from another faction that we were not at war with.
As we were not at war, they were in a loop trying to start the battle, but without success.
This continued until an enemy lord attacked the allied lord, and the neutral lord fled from there.
The game continued with lag for a few seconds and after that everything went back to normal, including the sound.
I could see that because it happened on my side. I tried to take pictures there but I don't know where they are.
As I play in a notebok, when this happened in the 2 new games that I started, the game almost stopped and froze, due to lack of processing. With better computers, I believe that there should only be a problem with the sound.