This happened in Codeforces Round #709 (Div.2)
There were some technical difficulties during the round and the main site was temporarily down. I had a "pretests passed" submission on question 1 at 0:03 mark, but the UI was not updating correctly so I re-submitted the same solution at 1:44 mark. In the end I was awarded 242 points for that problem and only my last submission counted.
https://codeforces.com/contest/1484/standings/participant/111374935#p111374935
I can't speak to what you're saying about the UI not updating, but the point calculations are working exactly how they should be. See number 8 in the rules.
Oh I understand thank you!
I had the same issue. The submit button was greyed out and not clickable. I clicked on it like 3-4 times and it was doing nothing. After going to my submissions page, it had already submitted the same solution twice.