Sometimes you can lose communication with clones and can't send any "Stop" request.
In this case, those clones stay in memory in a running state, and it is very hard to kill them. Stop or Kill launcher have no effect. The only way I have found is to close the project but it's not very usefull.
It will be good to have a watchdog mechanism to kill lonely clones
As discussed here JKI SMO and drjdpowell messenger library, have this kind of mechanism.