I have a 2011/12 Ford Focus 1.6 tdci titanium. I brought it with bad injectors, 2 of the 4 were changed at me, around 6 month ago. The car went great, I used it on long distances, came home, parked it for 2 weeks and when started to drive this evening the car made flapping noises when I accelerated. I had to stop after 5 min as white smoke started to emerge from the engine. Smome came even after I stopped the car and it needed like 2 minutes to fully stop. Car was towed home. My father said that he sees one of the injectors moving, while the other 3 is fixed and don't move at all. Could this be the issue? I am going to call the service who changed the injector (it was the same injector which now moves) or maybe it is something else?  White smoke doesn't have bad odor.

Has the coolant level changed?

No, engine oil, and all other liquid level is the same

If the injector moves enough to see, that cylinder will be losing compression.  Diesels rely on compression to burn the fuel, so that could just require tightening.  Or it might have broken the threaded stud, which would would then need to be drilled out before fitting a new one.

Can be you pisting ring