Exclamation Xperia P cannot find SIM card while charging

Hi,
my Xperia P started acting strange lately - despite the SIM being in my device, the message 'insert SIM card' appeared. After searching for a solution, restoring factory defaults twice and using Sony PC Companion to repair the installation, I checked with my operator just to find that the card was ok. Later i realized that the phone loses the SIM only when charging and only when it is over 90% charged (green LED light while charging).
Did any of you have a similar problem? I intend to return it on warranty, but not before i get a new phone (Nexus 5, here I come!). In the meantime, I'd like to find out what the community thinks of that

Cheers!