Help with Chain tension and sticking free hub?

Hi everyone. My freshly cleaned brompton all of the sudden is having two related issues as shown in the video. First is the loss of chain tension when back pedalled, which seems to be a common problem especially with 6speed C lines. It’s happened in the past after winter riding. But today a new second issue of a potentially sticky free hub has become apparent. When pushing the bike forward, the cranks arms turn. When washing the bike the other day, I used light degreaser on the chain and was careful to use a low pressure hose when rinsing. I let the bike dry off in the sun. I’ve seen several Brompton maintenance posts on here about this and have some things to try, however I wanted to add a clear video of the issue for others. I’m hoping to pick your brains on this one to determine any other causes .

Thanks to everyone in advance