You are NOT imagining this and I do NOT believe it is anything you have done to your phone. SONY had NOT bothered to fix it either as I have a Xperia Z5 compact and have the same problem. VERY FRUSTRAITING !!!!!! I am currently going to try the one fix mentioned above that turns on smart call handling where it answers when brought up to your ear. Haven't had a chance to prove it works yet. On this Xperia Z5, I went into 'settings', and then 'call'. In 'call settings' the very first choice is 'Smart Call Handling'. I turned it on and we shall see how it works! SONY should be embarassed to have not figured this out and came up with a FIX imediately. It obviously isn't just the screen as you well know because it 'senses' my fingers every other time for every other purpose. Just NOT to answer a call.
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