The friendly SW tech support staff helped me solve this issue today & concluded it might be a 2014-SP1 bug, so passing on FYI. We suspected graphics driver or SW installation issue, but turns out it’s not. Here is what I learned.

If you have a part built & use the roll back feature to a previous feature state & the drawing pointer remains in the left hand feature tree panel area with but with >>Show/Display mode on (flyout exposed) ... the part will not rebuild itself to that earlier desired rollback level. It just sits there in its pre-rollback state, almost like its calculating or hung up indefinitely. However, as soon as you slide the pointer back over into the drawing area, the part then rebuilds itself to the selected rollback level.

If the Hide/Display mode is off (collapsed << so the Show/Display fly-out is suppressed), looks like this issue does not happen.