Where to download the latest firmware on chuwi hi8pro?

Bought in the secondary market Chuwi Hi8Pro S / N PQ32G21160307971. Tablet with two Android and Windows operating systems. I have problems with the rapid discharge of the battery in standby mode, a non-sipped mode. I can not find the latest firmware. There are links, but the storage time of the files has expired and I can not get the information you need. Maybe I’m not looking there? Please share working links. Only as I understood, there are three modifications of the tablet, which differ in serial numbers. I am only interested in my serial number.