Thank you for using our online answers forum! I want to apologize for any inconvenience you have had with using HQ mode with your iOS applications. If this is only happening in HQ, chances are, you are not getting enough bandwidth (network speed) to stream in HQ mode. You can always get the speedtest.net application on your mobile device and test the speed of the network you are connected to. If it is anything below the minimum bandwidth requirements, that is most likely what is causing this issue. Below is a link that will tell you the bandwidth requirements for the Slingbox SOLO.
Hope this helps!
The Sling Moderation Team