Laravel 5.1 with Stapler doent work on iOS

We're making a website with Laravel 5.1. When we're trying to upload images it works fine for Chrome on Windows, and a couple of Android devices we tested it on. However; when we tried the application on an iOS device it gave a weird blank page (without any text, Laravel error or server error). In the debug mode it said that the server responded with a 500 error.

It's only occurring on some devices, with the same server and the same software. We tested it on an other server without ssl and then it worked fine on the iOS devices.

via Chebli Mohamed