I'm a total noob building a sammichFM. Finished all the soldering. All voltage tests OK, except that pin 13 socket on IC3 socket of the control PCB (74HC595) is not connected to ground as it is supposed to be referring to the build guide. I re-soldered the joint, but still no difference.  Should I simply run a jumper wire on the back of the PCB or am I missing something? Any other tests I should run or components I should look at?