If you don't need Android apps and just want a Kodi media center, flash LibreELEC. It runs faster than Android on the RK3128.
If you proceed to update firmware:
While the RK3128 ran Lollipop poorly, some users prefer the interface. This firmware is a hybrid mod by developers "Abdul_pt" and "Ricky". rk3128 mxq ep 68 firmware link
This is the tricky part. The device must be completely off. If you don't need Android apps and just