For some while I was unable to use my flashlight, a problem which I can live with...

However, when entering the Poseidon energy plant, my HUD-screen was shifted 10cm to the left while the surrounding world still remained where it should be. This means I can no longer see the status of my powerarmor, I have a huge problem with aiming and picking up items (because that is also displaced)...

How do I solve this?

You could upload the save and screenshot and PM me the links.

OneDrive, Google Drive, or Dropbox are good Cloud storage.

It's oké.

A cold restart fixed the problem.

Thanks for the help anyway!