What exactly do you mean by "render manager"? Is it Backburner or some other app?
Random idea, but it might work:
- open your scene
- go to Render Setup > Common
- unlock the small "lock" icon at the top of the window
- select the viewport you wish to render
- lock the small "lock" icon again
This is known to cause various issues and sometimes doing this helps.
Other than that, you were experiencing the "freeze unless VFB is moved" issue in the past. Could it be related? Did you manage to somehow get rid of it?
You are also welcome to contact us at
https://support.chaos.com/hc/en-us/requests/new and share your problematic scene and full logs.