If you came across with the same error like me with the "Transaction Broadcast Error" while you're posting, just stop trying re-post again and again. Go back and check your Blog, you may find that the post actually had been submitted successfully. Just like my case shown as below:
By now, unfortunately, there's no way to delete the post, and what you can do is edit the content and update the post, just like what I'm doing now.
I sincerely hope you'll not meet this problem, but if you do, I suggest editing and updating the repeated content into a reminder like this to help the upcoming user to get away of this error.
Sorry for the trouble with repeated-post I made for the readers.