Has anyone else has a similar problem? While riding, I can hear a loud, creaking sound, clearly coming from the derailleur hanger. What could be causing this? A cracked frame? The sound disappears for a few kilometers after I spray the derailleur hanger with multi purpose lubricant like wd-40 but then it returns. I've tried lubricating all the contact points between the hanger, the frame and the derailleur with grease, but it didn't help, the sound persists, making riding this bike unbearable. Here is a short video showing the problem:

https://youtube.com/shorts/gzvQ6XDUWGA?feature=share