Yep you damaged it a bit . I would find a replacement screw.. Yes it looks light enoughThank you for replies! Maybe the uniformity is related to 38 vs 357, which might have harder primers? Or is it also slight off-centerness of some strikes?
All was factory ammo (Magtech, Geco, S&B, not a wide selection available for me unfortunately).
I had tried tightening screw (in fact even damaged it a bit). Does it looks tight enough?