title_body: How to fix OSD flickering?
upvoted_answer: I fixed it by adding a common ground between the 5v regulator and the flight controller. I can't explain the science behind this, but I took the answer from this video from Painless360
  
  The flickering is completely gone, even when I punch the throttle.
  
  New wiring diagram:
  
  
  EDIT: I will leave the post unanswered until someone intelligible explains this, and maybe other OSD flickering causes just to keep the post general to the question and not specific to my hardware and wiring.