Update: it got so bad that I had to call guest services around midnight. Staff was awesome and gave me a vacant inside cabin for a good night's sleep.
They also told me that it's a known issue with the anchors on the Prima: swell/waves and the ship's movements seem to let the anchor bang against other ship's components, leading to this infernal noise.
So I suppose all front facing suites like mine could be affected, if swell/waves are at a certain strength.
Hope it helps.