Sorry for the late follow up, wasn't sure when the post would be approved so I got wrapped up in other stuff.
Thanks for the welcome!
To clarify: yes my books lay flat when they are out of the bag. I included some oddities in the pics tho just for larger sample size
Agents of Atlas is slightly wavy out of the bag, but even more pronounced when inside
Luna Snow has the very slightest spine roll forming, but when in the mylar it has that weird wave pattern.
The Brightest Day and Marvel Boy are completely flat out of the bag as most of my comics are- but when inside they seem to get wavy or the middle of the comic seems to stick out (if you look at the middle of the Marvel Boy cover this is what I mean if it makes sense). But if the rise is what is supposed to happen then maybe I won't worry lol.
I thought it was static or something- I had one batch where the mylites were all oddly tight, but I've bagged more than that batch. I notice modern marvels with the crappy paper seems more susceptible to this than older comics with thicker cover stock.