Z3735G update to 0x838 microcode causes tablet to hang at boot

While running Linux on a [Glavey TM800A550L tablet](https://www.aliexpress.com/item/32837708061.html) I noticed that it hangs at boot, sometimes showing various color patterns on the display, suggesting that the processor is writing over random memory, including the framebuffer.

It took me a while to figure this out, but adding `dis_ucode_ldr` on the kernel commandline fixes this. This is quite a sever bug, at one point in when I forgot to add `dis_ucode_ldr` on the kernel commandline the CPU overwrote parts of the memory-mapped SPI flash which contains the EFI nvram variables, including the Setup EFI variable which contains the BIOS settings. After this the tablet would no longer boot at all. I eventually managed to unbrick it without needing an eeprom programmer by using [DNX mode which still worked, see the blogpost which I wrote on this](https://hansdegoede.livejournal.com/25342.html).

The BIOS on the troublesome tablet comes with ucode version 0x830 and the attempted update (which breaks things) tries to update it to 0x838. Perhaps there is a problem with the specific jump from 0x830 to 0x838 ?

Note I have an Acer S1002 tablet which also has a Z3735G processor and there the microcode update works fine.