Sound bad, but maybe there is way here. Does the laptop function/light without batteries and only external power connected? I’m assuming, it should work without any batteries installed.
Also does the external power function well, need to check that. But since you mention barrel jack, you’re using external PSU. And those normally use attachable power cable, which may dislodge over time, make sure it’s well seated.
Edit: Here is short discussion about running Classic Reform without batteries. Is it okay to remove the LiFePo4 18650 cells?