There is a couple of things I would do here:
* Installing this gem of an app! [https://www.coconut-flavour.com/coconutbattery/|CoconutBattery]. Take a snapshot of the apps main window and post it here for us to see [guide|21499]
* Getting a USB-C power meter like this one [https://satechi.net/products/usb-c-power-meter?variant=31043692041|Satechi USB-C Power Meter Tester] So you can watch a bit better what is happening with your charger.
These will allow you to see more clearly what’s happening with your system. I do have a few questions which might offer us some clues on whats happening.
* You talk about having access to a second system what is it? Is the charger the same or different?
* Are you using the original charger and the USB-C cabe that came with it or using something different?