What also helps is seeing if your lock starts to turn slightly after you set a pin. This can happen for 2 reasons.
One: You caught the plus on the spool / security pin as described above. this means you haven't actually set it but just caught it the sheer line. if you push it up further it will force the lock turn back a bit making it easyer for other pins to reset if not carefully done.
Two: You have a mechanically dodgy lock where the holes in the plug aren't aligned nicely with the holes above the sheer line. Pushing up a pin can cause the lock to turn back resulting in the same issue as with example one.
Tension is the key here, if you want a good lock to try this principle on I suggest for example an Abus 55/50, they contain all spool pins and are great to practice on
They are tough for beginners so don't get frustrated
The good thing is with these padlocks you can actually hear the pins resetting and thus know you've messed up the tention.
The one bought had 4 spool pins! Only one or two would false set consistently, but it gave me great practice at how to sneak a false set spool past the shear line without reseting others. It is definitely all about the tension.
