On the box that fails to power off, can you please test -rc8 with these two
commits reverted:

commit 5a50fe709d527f31169263e36601dd83446d5744
ACPI: suspend: consolidate handling of Sx states addendum

commit f216cc3748a3a22c2b99390fddcdafa0583791a2
ACPI: suspend: consolidate handling of Sx states.

and see if it works?

I had done these tests in the first place (see my first mail), so yes,
reverting makes the box power off fine.

Will test this evening the patch you pointed in your next message.

-- 
Damien Wyart