Why are you making posts in notepad before transferring to the forum?
The forum has given me enough space for writing the post. I know it very well. But I have noticed many times when I posted in the forum post box I forget to put back button pressure, so I have to rewrite again. That is why I use my notepad according to the forum’s Tropic I create replay posts on the notepate, copy from there I post in the forum post box. And I do it comfortably, so I never made a mistake. But I did not understand how a post was submitted twice.
What we need to know now is how you are going to solve something that you did not understand; there is a possibility that you are going to make the same mistake.
So changing the way you post is, I believe, the answer, like previewing first before you hit the post button and checking your post history if you post the same post that you copy on your notepad.
I believe you are in a hurry to make a post; that usually happens if you want to increase your post count in a limited time you had.