Why is my keyboard light flickering and turns on and off?

Yes, liquid damage could explain the keyboard backlight flickering or not lighting up part of the keyboard.

As far as the charging, that might be normal! You would need to monitor the batteries temp to see if the thermal threshold was hit so the battery needed to cool down before it could be charged some more. I would use TG Pro or some other similar monitoring app which can allow you to track the batteries thermals and using a USB-C power meter inline with your charger a quick way to see what the charger is doing at the given time point.

You may want check the batteries health as well I find this gem of an App is a great tool CoconutBattery