https://bugs.freedesktop.org/show_bug.cgi?id=93826
--- Comment #41 from iuno@posteo.net --- I just downloaded and tried with a Linux Mint 18 image. Using kernel 4.4.0, the problem definitely DID exist back then, in contrast to what comment #0 suggested. So bisecting from 4.4 would be useless.
Are the DCEs affected by firmware files? Is it possible that the problem was pulled in from there?