Message: This is something that is caused by local user browsers which holds on to the data of a post if it was the last time the browser was on *this* page. Somehow, this data is retained in the browser and when you next go on to the page, the browser will ask if you want "resend the data". The best way to answer that is "no", because when you say "yes" to that question, this is what causes the duplicate postings.
Not being a web master I don't know this for sure, but I *think* the web page might be able to instruct the local browser to empty the data it is holding for the last "post" on *this* page before displaying itself to the user.
Call: K2MF 2/1/2021
Email direct response to k2mf.bgs@gmail.com