After all the talk I thought let me try Juice Defender Ultimate again and realised why I stopped using it the first time. I have it set to connect wifi/mobile every 10 minutes to check for emails and sync etc. I just switched my screen on after not looking at the phone for over an hour and 6 Whatsapp messages came through, some 45 minutes old. Now surely the whole "connect every 10 minutes" thing should mean that I get these messages?
FFS. I had the exact same issue today. It went further in that I had all of my calls directed straight to my voicemail this morning. Only at 15:00 did I get notification about these supposed missed calls and by the it was too late.
I'm selling this piece of schit now. Sick and tired of it...