found this strange bug. With browser like Safari or emulating mobile on Chrome, i found that controller method on init of the page is called 2 times, like if viewer try to refresh his page to do something… Another strange thing it’s that it doesn’t act like this for all kinds of file but, for example, with pdf, png, doc and ppptx.
This issue can be replicated with demo project, putting a breakpoint in Index method of HomeController.cs of GroupDocsViewerMVCDemo. If useful, i’m running it on Visual Studio 2013 ultimate.
Need for a response as soon as possible because this strange behaviour cause errors on viewer opening with the browser i said before.