Two weeks ago I had an issue about my brakes QR not working and asked about on this site Road rim bike brakes don't open when using the release
I got some help - and I am very thankful for that - pointing at replacing my cables. I did so and cleaned the brakes in the process. I followed the Park Tools book for that. During the first ride the rear brake opened, and since then I have not been able to close it. See this video https://i.imgur.com/RouHYPP.mp4
It looks like the mechanism which is supposed to maintain the brake closed has gone too soft.
