Lansinoh Breast Milk Storage Bags

I have a great baby sitter.  It was brought to my attention that the bags that I had frozen my breast milk leaked when she thawed them.  She had learned to start watching the bags.  There was one day that I had to run over my lunch break because I thought that my baby sitter had enough milk.  It turned out that she only had like 4 oz.  I like to leave enough milk with her just in case if Savanna wants 2 bottles while I'm working.  She told me at that time that another bag had started leaking and she caught in time.  (I like to think we are both together in seeing breast milk get wasted.  It breaks our hearts to even see 2 onces go down the drain.)  She won't be using the brand that I use because of the problem I'm having with these bags leaking.

The brand that I use is Lansinoh which I consider a "name-brand".  I have told Savanna's father about this problem and he says that he hasn't had a problem with them while thawing them.  He also doesn't think that the problem is with how long they have been in the freezer, the problem lies in the way that the bags were made.  So not sure what's up with the bags but I thought I would pass this problem I have had on.