Hi,
As i understand, you have a locked viewport for rendering, and everything works fine at the first seconds of the video.
Then what you to, is you change the viewport layout (you are not maximizing a viewport, but changing how many viewport 3ds Max draws) and this possibly messes up with the viewport lock and IR.
Instead of making 1 single viewport layout, try maximizing it (Alt + W by default) and see if the IR restarts after that - it shouldn't, unless you change something in the scene (but you can freely move in the viewport).
