Asus’ new ROG Ally software is broken. The brand new ACSE 1.5 software is entering a never ending install loop, but thankfully some ROG Ally owners have figured out a fix [also here in comments]
Big scale? Contract manufactured junk running software that is actively developed. A change in the steam libraries, probably due to upstream changes broke the static hardware. Eventually it will be a brick. It doesn't matter that it runs windows. The only thing that matters is that steam is actively developed and maintained.
Small scale, likely an API change with some workaround hack in the device code that could not account for the change in the Steam API.