I think you might be wrong here Kiki, a majority of the people (including me) that had this "popping/creaking" issue solved has stated, that the popping stopped when they got both their display assembly together with the topcase exchanged.
According to the Apple guy that repaired my laptop, the topcase (that is indeed a part of the palmrest) is connected to the screen assembly, thats why they exchanged the topcase first, in the end they concluded that it was a combination of both the topcase and the screen assembly, that made the popping/creaking sound.
https://discussions.apple.com/thread/7825434?start=480&tstart=0
However, it might very well be that the popping will return after a few weeks, but at the moment it seems like the only viable solution is to replace these parts, because replacing only a separate part clearly did not stop the issue.