Default Sound mode changes to Sound+Vibrate at midnight

I'm using the notification power widget buttons to change sound modes on my phone.
I usually tap it to change it to Silent at night (no vibration, no sound) but sometimes a call or a message would wake me up even though I had set the phone to silent.

I recently discovered that the phone changes to Sound+Vibrate at midnight. I'm using this ROM but I have no idea if that's what is causing the problem.

Anyone else has this issue?