Comment 39 for bug 43745

As a continuation to my previous post (see above).

After removing and replacing the coin cell battery, the laptop started booting again.
(not that I did like to this again, as I had to remove the keyboard).

Also, Grub is once again able to count down and boot automatically.

[...]

FYI: Turns out that Dell has a BIOS diagnostics tool for download (works as a bootable ISO). I would like to suggest to folks with this problem, that are still able to boot, to try using it; in order to help diagnose this.

I'll try it if grub's countdown stops again.