The relation between the StaticHeaders
and service parameters passing is really strange as the both functionalities does not have any common points ion the RadGrid source. Also I'm not able to replicate the described issue on my side even when the static headers are enabled. See my test movie below that presents the correct functionality on my side:
I suppose that there is something specific in your project that is leading t this strange behavior and the best option will be to open a regular support ticket and send us isolated runnable version of the application. This way we will be able to debug it locally and advise you further.
Check out the Telerik Platform - the only platform that combines a rich set of UI tools with powerful cloud services to develop web, hybrid and native mobile apps.