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The phone was launched 2007, so to be fair the phone close to 20 years old. There could be many reasons for the problems you experience, but likely age related degradation of the bonded connections to the screen from the screen drivers. Is the stripes changing when you put pressure on the screen? Think the only way to repair is to get a "donor" screen from another Serenata.        

IIRC, The Senenata (I had one with the same issue - cant remember where it is or if I binned it), had a custom screen. It was one of those things where B&O / B&O engineers did not give any gravity or consideration to replacement parts or longevity of component supply. They simply wanted a custom (and very expensive) screen of a specific given size. They did not care how long that component would be in production/could be made, nor that a GBP450 class phone would become an extreme GBP900 phone. Complete lack of consideration of world mobile phone economics in their engineering philosophy. One of the key reasons why they have been in financial difficulty for a long time.