I am able to pick the "ERA" pin-by-pin, sometimes it takes me 4 minutes and sometimes it takes me 15 minutes, but I am able to pick it, which I am happy about.

But recently, I bought a pin-tumbler lock from a shop called "Wilkinsons" which I could not pick at all

Question is, if you have a sequence of high-low pins from one extreme to the other, is this the reason I am finding it hard to pick this particular lock without security pins ?