Kohler did have some issues with this gasket blowing over the years, They have made running changes to both the gasket and cover to eliminate the issue.
Since you didn't post engine numbers (sticky above this section) I can't check if your engine falls into this category, When your local dealer looks up the new likely updated gasket it may come as a kit with a new cover. Just install what he shows and don't worry about any other causes for now......
Originally Posted by piston slapper
You never learn anything until you admit you don't know it all...
"Why go out preserved when you can go out beat up, worn out, sliding in sideways screaming, Holy Sh!t What A Ride" !!!