Cannot shutdown CamelContext even call CamelContext.stop/ServiceHelper in another thread

Hi,
I am using Camel 2.8.2, sometimes the CamelContext.stop is not working if
there is inflight message that is retrying forever in the processor due to
exception. I assume that there will be force shutdown after the timeout...
but sometimes it do force shutdown but sometimes force shutdown is not
working... any idea?

thanks