BMG

So I have a really annoying tick tick tick or more of a whop whop whop sound from my rear left drum when ever I apply the brake. However this does not occur if I pull the handbrake slightly and then apply the brake pedal - all is quiet as it should be. Also when I am stationary and press the pedal the rear left brake unit makes a ticking/clicking sound. The harder I press on the pedal the more ticks it makes. Both sounds are different to each other. I have just pulled the whole thing apart, cleaned, checked everything and it all looked fine.The only thing i noticed was that the trailing piston in the cylinder was depressed further in than the leading side. No idea if this is normal or not. After reassembly, both noises are back. I am completely lost......any ideas as the what the hell is going on?? Maybe the self adjuster is not working correctly? I hate drums....why do they still use them!!

2011 MK2 Ford Focus.