It just happened again! And this time I recorded it on video, here is the video... what do you think?
After getting this error message I close the window and refresh and my BTC are gone and sent to another address, rip :[
That video kinda explains it.. It definitely looks a bug from their side if whatever @Adolfin says about the 5% thing is correct. I'm afraid this could be a small portion of a big attack by a middleman. It's literally modifying the address on the server-side. This isn't supposed to happen for a reputed exchange like Paxful.
Watching this case.