Ive had both of my North kites, every Naish kite I've ever owned, and EH kites delaminate.
How do you store your kite? Do you roll it like a poster or do you fold it flat like harmonica?
I was told by my kite repair friend that rolling a kite in warm weather streches the bladder around valves and it slowly unglues them. All the kites are affected.
I've never understood why folks roll up their kites until I saw a "how to" video on a manufacturers website where in that video it showed how to pack up your kite... basically roll up each wing tip to the middle. I've always folded mine from the tips to the middle rather than roll it... it's faster but it's harder to get in the bag that way. I think if you're not careful it's easy to roll it up too tight and put some pressure where you don't want it. If you fold it the same way every time you probably develop creases which may or may not be harmful. Tough to call.
As an aside I had a sleeping bag and I remember the instructions were very clear... do NOT roll it up... rather just stuff it willy nilly into the bag. The reason.... rolling is very hard on the stitching.
In the case of a kite... rolling wouldn't likely damage stitching but it could affected bladder valves if they're being squeezed to hard from a tight roll. You add a little heat and that might be the just the force needed to pull them off slightly.
I know that to get a valve off a bladder all you have to do is hold the valve under hot water and pull/peal gently on it and in about 40 sec it's off. Easy as pie. Heat and valves is not good.
The good part is if they do leak... for the most part you can easily take them off and re-glue them in place with a little work. I've done it several times on a friends kite. Depending on the kite it can be a lot of work.