Hi everyone, I have a Phottix TC-501 wired remote whose battery is about to die off. I have been trying to open the battery compartment but it is not moving at all. Does anyone know how to open it? I try to slide the small piece of plastic on the back, following the direction of the arrow but its not moving. The instruction manual did not mention how to replace and write in to Phottix customer service simply told me slide aside and pull?