External display flickers on one of the Mac ports
The 13" MacBook Pro has two Thunderbolt 3 ports with support for USB 3.1.  USB-C is the connector type.  There are no 3.0 ports at all.



The flickering you are experiencing sounds like a clock sync issue  (TDMS clock for the display, not the clock that keeps system time).

First thing I would try is rebooting with the hub/dock connected to the port that's giving you trouble.  If the problem goes away, then you've narrowed down the problem.

If it remains, you may have a hardware issue.  Before taking it into Apple, however, it might be a good idea to try out a different video adapter.