Strange 35d Injector Failure??

[AgentX]

My E70 35D with 140k miles on the counter started making a strange noise (knoking) at idle. I tried locating the noise and believe it came from somewhere at the back of the engine from upper-middle side. Cars drove fine, like before, but would vibrate a bit at idle while RPMs were stable. When touching the high pressure fuel lines connecting to the injectors, I realized #5 was vibrating much more than the other ones. The knocking appeared to be in synch with injector#5 vibration. I connected Rheingold and ran a test. CODE 459B Smooth Running Controller - Cylinder 5.
Injector#5 has correct resistance (approx. 180 ohms), harness from DDE to Injector was found in good condition. I decided to remove injector#5.

Injector core seems to be separated from injector outer part. Maybe picture below can explain this better.

Is it normal to have the outer injector part loose? And do you think this could cause the engine knocking noise? Is there anything I can do or need to buy a new injector?