There is a rate limit for submitting tag wiki edits. When you hit it, the "You can perform this action again in 30 seconds" message appears rather close to the Save edits button:
It could use a little more space, like e.g. the message you get when you don't reach the 6 character limit for regular posts:
While you're at it, it probably can use a period at the end. That's the new Stacks standard for error messages IIRC.