I checked all declarations and function calls related to the device`s definition as a Router. Also, I double checked how the power management of the device is handled and as far as I can tell it should never go into a sleepy state but stay idle (waiting for events) with rx_on_when_idle set TRUE.
At this point I am absolutely clueless why the BinaryValue cluster isnt read proberly… 
Concerning a custom cluster:
Is there a step by step guide on what to add where (e.g. cluster description in general.xml, modifications in deconz_rest_plugin etc.) so it is proberly read in the deCONZ GUI?