I’ve noticed since 1.6 that if my VFB IR reaches the pass limit I set in the render settings, I cannot restart it again via the VFB. The “start interactive” button in the render settings is also grey out, until I close the VFB. After that I can start interactive again.
So, I guess the bug is that you can’t restart VFB IR via the VFB after the pass limit has been reached.