How I fixed my Worx Landroid charging problem: Front charged WG754E red and green light

My front charged Landorid wouldn't charge. The docking station reacted (red light) when docking my unit, but after a while it started to change between red and green light. Sometimes it beeped for a while too. A new battery didn't solve the problem. When emptied the brand new battery did not charge either.
The video shows how to inspect the tiny cables inside the front metal plates. There are 4 wires, red, green, black, black (one to each metal plate). In my case one (black) of 4 wires was broken.
It's a common problem to this model.