..possibly a short in the power cord. Usually, it's a short at the computer's jack. Since you didn't tell us, I'll guess the Kogan techs are using a different power cord when they're doing the testing and as such, it might be the power cord but only testing with a new power cord would tell.

In the meantime, please try this and see if it helps. I doubt it, but it's worth a try. It's a two step process.

Uninstalling and reinstalling power management software in Windows:

In order to correct problems with the battery's power management software, follow the steps below.
1. Access the “Device Manager” .
2. Expand the Batteries category.
3. Under the Batteries category, right-click the Microsoft ACPI Compliant Control Method Battery listing, and select Uninstall .
WARNING: Do not remove the Microsoft AC Adapter driver or any other ACPI compliant driver.
4. On the Device Manager taskbar, click Scan for hardware changes .
Alternately, select Action > Scan for hardware changes .
Windows will scan your computer for hardware that doesn't have drivers installed, and will install the drivers needed to manage your battery's power. Restarting Windows will have the same effect of letting Windows re-recognize the hardware and installing the correct drivers.

If that doesn’t fix it, then shut down the computer, unplug all power cords, remove the battery, then depress the power button for 30 seconds. Replace the battery making sure all connections are solid, then plug in the power cord. Hopefully things are good.

Hope this helps.