Arduino Support pointed out to you this github issue (SimpleWebServerWifi hangs after a time in MKR1000. · Issue #72 · arduino-libraries/WiFi101 · GitHub ) where we are helping another user with a similar problem. You can speed up the resolution of this issue by providing our engineer with the code so he can figue out where the bug is.
@mephala see the above github issue. please help out by providing your code
People we're here to help but the only way to determine if the problem is in our code, Atmel's code or your code is by providing us with something that consistently reproduces the bug.