I shall give it a try at Amcorp service centre instead.

Only after my phone was soaked with water due to water resistance failure, it flickered but the phone continue to operate without issue.

Side is still better than back. Being blocked by palm is a matter of adjusting the palm whereas missing phone calls is likely with speakers at the back. Putting front sounds best but may not blend well with the design.

Sony said they found the faulty parts in my Xperia Z. They repaired it despite water went in, but the sticker spare part needs to wait till 22nd July. I couldn't get a replacement unit. It's hard to be confident that the phone will come back perfect after it proves that water resistance sealing is easily compromised and water has indeed went in the phone to cause some damage.