charging issue while using a type c powerbank to charge rog phone 6

[Cryoz]

when i charge the rog phone 6 using a type c powerbank(anker 10,000mah powerbank 20w) and using the main port of the device, charging it causes to switch nonstop from fast charging to charging back and forth. how can i fix this problem? But when using the secondary port ( for the aeroactive cooler 6 port) it works normally (displays as fast charging) 

seems the phone is confused to what kind of charging it needs

[sunnyp1187]

I found similar issue too. When using a power bank USBC port, the Rog says it's charging but it isn't. It is still running from its internal battery.