Auto-brightness service is broken. Possible attempt to fix was to built it from source rather than the using Sony blobs. It fixed notification light though.
However, no valuable information has been generated. With vendor blobs, sigprof said:
Apparently illumination_service has a bug it calls accept() without initializing the length pointed to by the 3rd parameter, and due to some uninitialized garbage there the call fails with EINVAL. I tried to make a binary patch to pass something acceptable to the syscall, and it seems to work, but obviously patching proprietary binaries is not a solution.