I think I have the exact same issue. In 4.17 everything worked fine with scale world to meters, but since the spectator mode doesn’t work properly when packaged we wanted to switch to 4.18… after migrating and updating everything this issue occurs when we try to shrink our player (using HTC Vive). The motion controller vanish and the distance between the eyes stays the same and disrupts the view greatly.
Recompiling our pawn didn’t do anything and I don’t know how I can fix this camera issue. Our small game also relies on being able to mess around with the scale. This issue pretty much kills the effort. 
------------At least this is what I thought until now! My Solution: ----------------
You don’t need to “recompile” or “resave” your camera-holding BP. You need to close every additional tab. Whenever I opened at least one additional tab besides my level the perspective got disrupted after changing the world to meter scale. Whenever I closed every additional tab and only had my level opened, this issue is gone. I don’t understand this issue and it is really weird, but hopefully I could help someone with my approach.