Help / advice regarding Dell Latitude 14 5420

Hey fellow fixers,

I am new to laptop fixing and recently got a pretty rugged Dell Latitude 14 5420 (256GB, 16GB) for 30 bucks. It was so cheap because the display didn't work. Since then, I have updated the HDD to 1TB and RAM to 32 GB. That seems to have worked well.

I am using it with disconnected bezel cable, otherwise, it didn't let me see BIOS to install ubuntu and then I kept it like this because resolutions are better (camera doesn't work, I use driodcam + phone for that).

However, I need advice regarding the following:

1. What component is broken when screen doesn't function?

Here is how it looks like in video / picture. Is this a screen issue or a connection issue. Note that it looks broken physically but there aren't physical cracks, this is just visual. If screen replacement doesn't work, I am okay with that (since I bought it to use it more or less like a PC)

2. This is slightly bigger issue. When I disconnect the device from AC power (USB C that does both power and display). The machine turns off. All the BIOS / OS level diagnostics show that battery is healthy and charging (I have also seen it discharge).

I am getting the following error code too. It continuously blinks this signature, however, 4 amber and 1 white is not listed on the manual: https://www.dell.com/support/manuals/en-...

Regarding 2, maybe that's 3 amber and 1 white i.e. CMOS battery failure, that would indicate probably why it turns off when AC power is disconnected? Diagnostics don't catch it though.

Happy to post pictures of the mother board. Please advice.

Okay, the 2nd issue is fixed with a CMOS reset. I just disconnected the coin battery for a minute and viola, the error code is gone and it works on battery now.