Are you ensuring the tyres are at the correct temperatures when you do a pressure check? If both the tyres are cold, and the ambient air temperature likewise then you will overinflate tyres which will lead to the centre strip wearing out.
For those who can deal with the math......
Tyre pressure and temperature
I've always run my Diamaris at the recommended pressure (2.2bar = 31.9psi [32psi for most of us]), and never seen the effect you have, but I have seen it on overinflated tyres where the pressure guage used for inflation was under-reading, or the wrong ambient temperature was used and not corrected for.