Do the other cases have ejector pin marks? Somewhere around that pressure level, the brass case head expands and the primer pockets loosen.

I have some that I loaded at max that did that. They were safe in the gun and ran well, but going back into the shellholder was a no go. Now I check every case head for this kind of damage.

I also load with a light crimp from a Lee fcd. That die is a collet crimper. Some length variation is ok.