Well you have 2 options now it seems to upgrade to 2.7.13 since it out. You are running the same version of miui on both systems? or are you mixing it? 2.7.6 on one system and 2.6.xx on another? I would recommend trying to run both systems on 2.7.13 if this do not work for you try Xiaomi Mi-one guide to install update.zip and Brush tool guide and re-flash the entire phone with the brush tool to see if that help.