Seems like I read about something similar to this a few days ago on here, but can't find it now.
Today I was working on a project and had 3 PRV windows tabbed in the multidock. One of the tracks (a midi bass) all of a sudden stopped auto scrolling as the cursor played passed the right side of the window. It was random though...sometimes it would scroll and sometimes not. When it was working, it would go back the the start point when when the space bar was hit to stop playback...which is normal. When it was not working, the PRV window stayed at the current location and wouldn't jump back to the start point as expected.
One thing I realized though...it was just one PRV track doing this....I could switch between the other PRV track views and they would auto scroll just fine all the time. It was just the one PRV track that was sporadic.
I looked all over the PRV track to see if it might be some setting I had inadvertently changed by mistake...but I don't think so since it was working ok part of the time and not the rest.
I recently updated my Nvidia video card to the latest driver and I'm wondering now if that may have caused this.