The Well Audio
Looks like K4 does not switch since the coils of K4, K3_1 and K3_2 are driven in parallel.
It seems that one of the tracks which drive the coil of K4 is broken.
Please, with a DMM measure the voltage across the coil of the three relais (pins 1 and 8) with battery on and off.
You should measure 0V and around 12V across all the coils.
If you have no voltage change across the coil of K4 but you have voltage change across the coil of K3_1 and K3_2, please check the tracks to the coil of K4.
They are on the boottom of the PCB, starting from the coil of K4, then D9, then D8_1, then D8_2 and so on.