After doing the mappings change did you do the following?
./imsimta cnbuild
./imsimta restart job_controller
iMS uses a compiled configuration to enhance performance. Every time you make a config change you need to run the cnbuild command to re-compile the configuration and then restart the process that would be affected by the change. In your case, the job_controller. If you made a change to the dispatcher.cnf file you would have to restart the dispatcher.
Just doing a ./stop-msg followed bt a ./start-msg will not do it as those commands do not re-compile the configuration.