You can attach any file in the forum, provided you zip them first.
You might have 2 possible issues, not mutually exclusive
A problem with the engine and the video driver, in this case the Slitherine Helpdesk will help you.
A problem with a game play bug or buggy historical event, in this case with your saved game we will check the issue and fix it.
That's abnormal to have any error message in the game, if you get one, we can help you one way or another. Some people are indeed bothered by bugs, some never see one.