I'm not the only one having issues.
Currently, on my computer and phone, when I post it will hang for a few seconds and then ask if I want to leave the page or stay on the page.
I click to leave the page and I get another post page with my text in it. If I click submit again I get the duplicate posting warning.
If I walk away and come back the post will post and I have a duplicate post.
If I just say I want to leave the page and then go back to the forum I can see that the post was recorded even though it wasn't displayed after posting it.