DAF XF 105 is no longer running out

Hello! Have a vacation right now, and just now our helper calls me, and says that he can’t turn off my DAF anymore He pulls off the ignition key, the ignition is off and the truck continues. My question is, can it possibly be due to the ignition key, because it is only intended as a reserve and the originals I have at my home?? The problem occurred two years ago with another helper driver, who also had only the reserve key! nor anything! He has already knocked on the relay (no.126) (unfortunately without success) For some useful tips I am very grateful! Greeting Eric