Been noticing this for a while now. The live viewer randomly starts the render from scratch when using things like post effects in the camera, selecting a material or even just moving the cursor.
Again, happens randomly and so far the only solution i've found is to restart Cinema, but even then sometimes the issue doesn't go away.
I'm on V4.02.1 - R2
Nvidia drivers 431.60 (recently updated from 417 but it was still doing it then and continues to do it now)
Windows 10
Here's a screen record of the issue
https://www.dropbox.com/s/n7pbzvsgn2kj3 ... e.mp4?dl=0