Vine server in El Capitan suffers from extreme whiteout

I upgraded to El Capitan and although I can still connect to the VNC server, the window is entirely white. I see no errors or warnings in the client log. I have found a workaround to get it working: start the built-in OS X screen sharing and connect to it once. The OSXvnc server will then suddenly start transmitting its image. This workaround does not survive a reboot and must be repeated regularly: it is best to leave the Screen Sharing VNC session open and wiggle the mouse over it every 15 minutes to prevent the Vine image from freezing.
Anyhow, this workaround does seem to indicate that the problem might be easy to fix…

The reason why I want to use Vine instead of the built-in VNC server is that Vine allows to trade off image quality for speed. My connection is slow enough that the built-in server is nearly unusable. Apple probably disabled 8-bit and low-quality JPEG to avoid any risk that customers would see a less than perfect image, but I couldn’t care less.