Running debian/sid on a Thinkpad E460 I have found a collection of (presumably related) problems since trying to upgrade to kernel 5.x Nothing like this has ever occurred with earlier kernel versions.
The symptoms are very simple:
On suspend the machine appears to sleep (fans stop, power light begins slow flash) but is unresponsive to keyboard or power buttons. The only way to start it up again appears to be to force a reset.
On hibernate, the machine writes the image to the swap partition correctly, but then instead of the power light flashing rapidly three times and the machine shutting down, the power light continues flashing indefinitely and the machine continues to consume power. I haven't measured the level of power consumption very precisely but overnight a full battery was completely run down. If I force a reset, the machine then resumes correctly from the image it wrote.
I also tried rtcwake, and with suspend to RAM and the machine did not wake as expected.
I've looked through /var/log/syslog and the final messages prior to suspending look like this:
Jul 26 21:36:44 thinkpad systemd-sleep: Failed to stop network-manager.service: Unit network-manager.service not loaded. Jul 26 21:36:44 thinkpad : /lib/systemd/system-sleep/network-manager failed with exit status 5. Jul 26 21:36:44 thinkpad systemd-sleep: Suspending system...
It doesn't seem likely to me that network manager would cause such a problem. Rather it seems that the kernel isn't communicating properly with the BIOS?
Can anyone offer any suggestions?