no one can answer your question correctly without knowing all the details of your system.
in regards to light curtains.
most light curtains have a spacing between the beams, some have closer beams than others.
Most light curtains allow blanking ( the ability to block part of the light curtain without tripping the light curtain.
when you break the light curtain, all motion should stop. the general rule is if you can put your hand in harms way before the machine stops, you must move the light curtain back more. when the light curtain is cleared, you must reset the light curtain. I cannot say in regards to sensivity, never heard of that before.
in regards to the e-stop.
when an e-stop is pushed, all power to the inputs / outputs must be killed and all machine operations are to stop. this may also require a quick dump exhaust air valve (risk assessment MUST be done - if you dump the air, you may create an even bigger hazard when the air is restored, thus the need for the risk assessment).
In regards to your incident, it all depends on the valve configuration.
are the valves single solenoid spring return, double solenoid open center, double solenoid blocked center, double solenoid with p to a and b, detent valves?
you must look at the valve powering the air cylinder to find out what the nature of the cylinder will be once the valve is energized and you hit the e-stop or loose power. That's the only way that I know of.
for example, a detented valve once energized, will stay in that position until manually reversed or power is applied to the other valve. if the valve was energized and the cylinder was going to the crimp position and you hit the e-stop, the cylinder will continue in that direction until it hits something or the cylinder bottoms out. a quick dump exhaust valve would release the air pressure and stop the cylinder, BUT !!, when the air is reapplied, the cylinder will move in that direction.
that's why I say that you have to look at the valve and determine the nature of its actions.
james