Have you tried the Telerik Verified Keyboard Plugin
? If not, I suggest you try it out and its disableScroll() method. To install the plugin directly into your project, right click on your project -> Manage Packages -> Plugins Marketplace -> Select the Keyboard plugin and click install. Of course, you will have to disable the core Keyboard plugin from Properties -> Plugins for this one to work.
Try this out and let me know the results.