Comment 33 for bug 1763273

One further historical detail: when these machines were running 14.04.3 and we made the mistake of accepting the HardWare Enablement (HWE) upgrade:

https://wiki.ubuntu.com/1404_HWE_EOL

which replaced the old fglrx driver with the radeon one, that's when we first encountered this unable-to-unblank problem.

Fortunately, at that time we were able to roll back Xorg to 1.16 and keep things sort-of working:

https://askubuntu.com/questions/815591/ubuntu-14-04-5-16-04-and-newer-on-amd-graphics
https://askubuntu.com/questions/676216/downgrade-xorg-server

When we performed a clean, full re-install with 16.04 we were hoping this problem would be resolved, but as I've documented here it continues to affect the systems.