I had a similar problem and here is how I fixed it. You will need access to a lathe for this.
First I faced the gasket surface flat. Then I machined the gasket surface again another .004" but I stopped just after the bolt holes leaving a ring about .125" wide. You can see in the photo. It's the red ring. Now when you tighten down the bolts it pinches the gasket in place.
I realize that not everyone has the ability to do this but it's worth the trouble to find a machine shop that will do it for you.
Ted
View attachment 1715031826
