We had a Switch come through today that would not show an image while in the dock. We found that the charge port has been attempted to be repaired by someone else.

3 or 4 pins were loose/floating and had no contact with the corresponding pads on the motherboard and 2 of the pins were shorted together with solder that should not have been there.The side effect of this we found was the switch would only charge on one side of the charge cable and it should charge both sides. This could also be the reason why there was no picture when on the dock.

We replaced the port which fixed the one sided charging issue but the no picture while docked still persisted. This then leads to the PI3USB chip which controls the HDMI picture through the port.

Once the PI3USB IC was replaced we had picture through the dock. Another happy customer