All of the above.
i find that if the scales are too loose when open they move as i shave ...unexpectedly.. and i get nicked.

too loose when closing you are bound to hit the scaled...

if the scales are loose.. i would rather it be near the closed position than the open position.. and yes they can be tight in one and loose in the other... bent pins and heavily tapered spine widths can make it a problem...

when you tighten pins always check to make sure they are tight in both the open and closed ranges.