On a Thinkpad W530, running Debian 10 (with XFCE):
The screen turns black after closing and opening the lid, and stays black. The computer remains on and is working, it is possible to SSH in over the network, no errors in dmesg.
After closing the still black screen for a second time, the computer enters into sleep mode (the sleep LED turns on).
Opening the lid the second time makes the display turn back on. This happens fast, hence I believe the sleep mode is ACPI S3 (suspend to RAM).
I've attempted to install the nvidia prorpietary drivers, sadly, same problem.
What should I do? I've tried to poke around in systemd's logind.conf, as well as in XFCE's power management settings, it is set to "lock screen" both on battery and on AC power.
The first time the lid is closed, if I attempt to switch to a virtual terminal with ctrl+alt+f1, this succeeds. I am able to switch back to X with ctrl+alt+f7, but then I'm greeted with "This session is locked", and it is completely unresponsive.