I think Sian has hit the proverbial nail. It is down to concentration.
Get yourself a pre-shot routine, whether that be lining up the writing on the base of the cartridges or what ever works for you, but something that helps you clear all other thoughts from your mind and lets you concentrate on the task in hand.
Eventually this routine will become a subconcious trigger for a particular mindset, so that once you start to do 'it', your brain switches into concentration mode.
I think that half the problem of the 'easy misses' is not 'being in the zone' when in the stand. Something that I am just learning to do now after about 20 months of practicing to get there.
For me it starts just before I go into the stand when I move the amount of cartridges needed for that stand into the front section of the pocket on my vest, and carries on until I exit. I have been known to back out of the stand and go back in because I was distracted but thankfully not often.
It doesn't matter what your routine is, so long as you always use it. Strange at first because it feels like it is something else to remember, but it soon becomes habit. From there, as you train yourself to concentrate when you do it, it starts to become your mindset trigger.
Just my opinion of course, and plenty of far better shots (than me) on here will have their own methods which I am sure they will share.
Hope that helps.