Question about cards bending inside binders

I recently sleeved all my cards with sealable perfect fits a couple weeks ago and it was fine. But just now I checked my binder and I see a decent amount of cards bending, not all but maybe like 25%. Ima causal collector and just collect for fun, only have a couple big hitters. But still wanna know if this is caused by my binder, storage, perfect fit sleeve, or anything else? Type of binder I have is on image 5 submitted by /u/itachirated [link] [comments]