Just a thought but are you shooting on an outdoor range? I've had amazing results on a warm/dry/NO wind day. Then, a week or 2 later my groups opened up almost 2x. When I was looking at the targets (100 yds) I realized there was a small breeze dropping down the hill and across the range. The groups had a lot more horizontal dispersion than vertical and yes the group was blown across from the wind direction. If you happen to have a wind (even a small breeze) coming from 11 oclock, then switching to 1 oclock, you're in for some nasty results. Just a thought.
I live on an acreage and I shoot from my deck and my yard has a decent shelterbelt. Since I shoot from home I can shoot almost any time, I scan the weather forecasts for some calm days and try to take advantage of them. I cannot eliminate wind from the equation but I do try to minimize it.