USB-C Charger only charges one way, not reversed
So, I've got a MacBook Pro (13-inch, 2017). The one without TouchBar and only two USB-C/Thunderbolt 3 ports.
My original USB-C Charger works in the bottom port perfectly. In the top port, when it lies naturally with the bend of the cable, it is making the 'charging chime' and showing a lightning bolt in the battery icon. it says "Battery Not Charging" though. Flipping it over so it lies naturally, it is neither making the charging chime or charging at all. Again, bottom port works perfectly. Also when connecting to my iPhone XS.
The upper port does not work at all when trying to connect my iPhone XS using USB-C to Lightning cable. (Bottom port works perfectly).
Is this an issue with the upper Thunderbolt 3 port, or is it an issue with both of my, relatively new, USB-C charging cables?
MacBook Pro 13", macOS 10.14