JB 4S won't wake up from standby

I have a jailbroken 4S on firmware 5.1.1. Recently it has this weird problem. Sometimes (not always) it can't be waken up from standby (home button and power button don't do anything). I use a lot of "touch" tweaks so I'm sure the physical buttons are rarely used and in good condition. The problem is definitely software.

Did anyone experience this recently? What JB tweak did you install recently that causes this?

TIA