Hi

I have a Dell 5570. It supports up to 4 external monitors according to the Dell website KB article.

The laptop has a total of 3 USB-C ports. Two on the left side, one on the right side.

I have 3 external monitors connected to the laptop: one is connected directly to the laptop via a USB-C cable (displayport alt mode) and the other two are connected to a Thunderbolt dock which then connects to one port on the laptop.

The only way I can get all 3 monitors to work at the same time, is if I use one port on the left side of the laptop, and one on the right.

Why won't it work if I connect the monitors to the ports on the left side only? 

Ideally I'd like to only use the ports on the left side of the laptop.

Can you help me understand?