Nesting a [show_post] inside a page with posts and using the same selection criteria is problematic.
I could not recreate your exact problem, but I tried a similar nesting and got an essentially blank screen (just the header and menus) as the nesting caused an infinite loop.
I don’t know if there is a solution for this. You might need to add a tag instead of a category so you can use tags and categories.
Also, try different values with the show post (full vs excerpt, for example.)