I just bought 3 sheets. 2 are air tight and 1 seems to have lost this ability. Does this some times happen or could it be something more sus?
Could have had a bump thats caused a tiny hole somewhere that's let the air in is my guess, have a very good look over the entire packaging
Yep, some bags are vacuum sealed tight, others are loosely sealed... others are re-sealed. I have a preference for the vacuum sealed ones... their capsules don't roll around with handling.
I have seen this too and only ever seen 3 sheets in person and 1 of the 3 was not a tight seal and air was in the package. It probably wont hurt anything but of coarse air tight is better for long term storage if you are concerned about mild rim toning. I personally like toning on my coins if its natural