It leaks in the microwave

The silicone seems to be of good quality, but I can’t say I love this sterilizing cup because 1- it’s not easy to fold it back 2- I didn’t fill it all the way up with water, I just used enough water to cover most part of my cup and still, after microwaving it opened and leaked (as I show in the picture). I had read a review saying the same thing before but I chose to give it a try anyways, so I guess it’s my fault.

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