The only correlation I've managed to muster is the Wifi. I think it happens if the Wifi goes down while the phone is connected. I think it also happens if I switch access points (for example when I move to one building to another at work).
It appears as if something related to Wifi is stuck in a busy loop or something. My only graceful exit out of the problem is to reboot the phone. Often I couldn't act in time and have had missed alarms and such.
I also know that it's a recent development; something that I've noticed happening only for couple of months. I'm thinking of resetting the phone to factory settings and starting over again. Before I do that I thought I'd ask around if this sounds something familiar or tastes like any known issues. Is there any diagnostics or logs that I can provide? Or are they any apps that I can install that can tell what's eating the battery so fast (currently it's telling me Android OS!)?
My phone is Karbonn A9+ (bought from India) and runs Android 4.0.4.