@helpmelefty, Actually the two sides of a USB-C connector are not identical; they actually use different communication channels depending on which side is up. Here are a couple of images courtesy of allaboutcircuits.com.
Figure 1. The USB Type-C receptacle. Image courtesy of Microchip.
Figure 2. The USB Type-C plug. Image courtesy of Microchip.
You'll note that the TX/RX pins actually have two separate channels that get swapped when the connector is flipped. There are two different channel configuration (CC) pins as well, so it's entirely possible that some circuitry works differently in one orientation vs. the other. For example if one CC pin is bad but the other is functional, you can get high power/fast charging on one side but not the other.
It sounds as though on your phone there's some kind of problem with the fast charging circuitry, but it's impossible to say exactly where the problem originates; whether it's the charging port on the motherboard or perhaps the power management chips. Unfortunately the USB-C port on your phone is mounted directly on the motherboard so replacing it requires specialized equipment and microsoldering expertise; it's generally not something us home DIY-ers ourselves can tackle without a lot of practice.
At this point I'd say your best chance for repair is to take it to a shop; a good one should be able to diagnose the problem and give you an idea of what it would take to fix it.