I can’t find an active thinkpad centric community on here I am just going to post here. My Thinkpad T480s, 16 GB RAM, 238 GB SSD is randomly shutting off while at like 50%. When I try to open it back up it always is dead and I have to connect charger to boot it up again. Why is this happening? Is it battery issue? It complains about not being able to read temp2_input while shutting down and sometimes say PM usage count underflow. Not sure what that is supposed to mean.
Are you using battery thresholds and keeping your laptop connected? There is a bug in ThinkPads, at least with my t480, in which the batteries get discharged over time but doesn’t get reported which causes the sudden power off. If you are using TLP I suggest you to either force a full charge or a recalibration to charge your battery properly. Also don’t discard the possibility of having a broken battery.