We have had several reports via support and here on the forum of this issue and working towards resolving it. However, reproducing this issue has been difficult. If you can provide any reliable steps to reproduce this it would help tremendously in solving this.
I will update this thread as I gather more information.
Currently, I have verified the app is not doing anything on resume so not sure what would cause it to lock up. One idea I am exploring is moving to WKWebView (currently using UIWebView).