Yes, it's endemic to the supplied charger rather than being a fault of the device, and no, there's no workaround that involves using that charger.
There are numerous posts here reporting that usb chargers for other devices (or generic chargers for multiple devices which include a mini-usb adapter) charge the tablet as well as the supplied charger, but without causing spurious input. The snag is that you can't have something else (such as a 3G modem dongle) plugged in at the same time. Charging via the supplied usb lead from a PC or laptop isn't a solution, because the charge rate can't keep up with the depletion rate except under very light use.
Thank you very much, I tried charging the tablet using a usb charging wire plugged into a mains adapter and it seems to be working fine. Hopefully that does well in terms of charging it properly too (in comparison to the pc/laptop based usb charging). Also, thank you for the general effort you invest into the forum M.Beddow, I am finding quite a few posts from you here and there very helpful.
Glad to be of some help. If by any chance you find that the usb charger doesn't seem to be charging on a par with the dedicated charger, it's worth trying a different charger or lead. Some USB chargers aren't wired in the way needed to "tell" a smart usb port like the one on these tabs that they are indeed drawing current from a proper charger, not a PC or suchlike. Without that "assurance" (actually conveyed by the way the pins intended for data transfer are tied to ground) the usb port limits its current drain so as to avoid exceeding the current rating of the PC usb port it assumes it's linked to.