video playback on ios 11 doesnt work

since the update to IOS 11 we have a problem with our App, we released for a customer in June, 2017. Basically its an Html5 app, which is converted with cordova (intel XDK) to launch it for the app store. Until the intel XDK isn't supported anymore, ive changed to adobe PhoneGap - I thought there could be an problem with outdated frameworks. But I have the same result on each device with IOS11.

The Problem:
We recognized an problem with our integrated Video file, wich was working on all previous IOS versions, so if you´re using a device with IOS 10 installed it works - it seems to be a problem with the new update. So now, on IOS 11 the video (intro) isnt playing. To determine the problem, ive created a blank project in the html5 engine (construct2) and build it for IOS too (adobe PhoneGap with cordova frameworks we were using for this version. Screenshot in attachment) - with the same result. So basically we have no idea what could be the reason for this - and so its the reason to write onto your support. I also wrote an e-mail to the apple technical support, but they told us to contact the engine developer. Probably there is an outdated or not supported framework/plugin for IOS11.

Link to the game (IOS):
https://itunes.apple.com/us/app/szkb-kabi/id948237518?mt=8
After the start button right at the beginning, an video (intro) should appear (you can see a red x in the upper right corner) - but on IOS 11 devices there is only a black background.

Hope we can find a solution, or a workaround for this one, because this issue should be a general problem.

Original answer from apple (not helpful at all):
"We've determined that your question should be addressed by the support channel for Cordova - the third-party resource you are using. DTS supports developers using Apple-authored tools and frameworks only."