Evidently the bug I filed is a duplicate of this (1634242), also with T420s laptops. But I don't even have to put them machines to sleep or even wait. All I have to do is lock the laptop and it crashes.
FYI, I don't get this with Ubuntu, Ubuntu Gnome, or any other derivatives. I tried a newer kernel with the same effect.
Evidently the bug I filed is a duplicate of this (1634242), also with T420s laptops. But I don't even have to put them machines to sleep or even wait. All I have to do is lock the laptop and it crashes.
FYI, I don't get this with Ubuntu, Ubuntu Gnome, or any other derivatives. I tried a newer kernel with the same effect.