Comment # 1 on bug 1017504 from Takashi Iwai

The message is just a red herring.  It merely shows that the system skips the
signature verification of the hibernation image (basically for Secure Boot).

Try the hibernation with the newer kernel in OBS Kernel:stable repo.  If it
works reliably there, there is a change to fix with openSUSE 42.2 kernel, too.