nandohyphen1 I'll try and go to a repair shop next time I'm in the city if I have a chance.
Until then I suspect it makes sense to treat this as likely an issue with the USB-C hardware. It is very plausible that physical shock can influence the quality of the physical connection, and fairly unlikely that physical shock would influence the behavior of the charger, or the USB-C controller, or the relevant device driver.
And the particular hardware issue I would suspect -- especially since some cleaning of the port resulted in a partial improvement to charging -- is debris/grime in the port.