Trying to RNG for perfect IV Zekrom using Standard (No C-Gear).
So far, I've been able to hit the seed consistently and catch it, matching the IVs for the first frame of that seed. I need frame 6, so I reset everything and hit the seed again with five pokemon in my party. I walk 128 steps then engage Zekrom, catch it, and the IVs aren't even anywhere close - I can't even find them in the seed's other frames, or even in the frames of nearby seeds (+ or - a second).
So I reset with two party pokemon, walked 128 steps and engaged Zekrom, caught it, and it matched my seed's frame 3 IVs. So what's going on? Is there a variable or rule that I don't know about? I've tried twice - I'm about to try again.