Dell Latitude 7490 invalid memory installed problem

I'm getting a 2 amber - 5 white LED flash sequence issue in my Dell Latitude 7490. The issue arose when I was using my laptop then it sudenly froze. I forced power-off by holding the power button then it atarted happening.

I've tried every solution and every combinations of it I could possibly do. What's weird is that I'm still getting the same 2 amber - 5 white pattern even if there isn't anything plugged (no RAM, battery and CMOS disconnected). I should be getting 2-3 pattern according to this [Owner's Manual](https://www.dell.com/support/manuals/en-us/latitude-14-7490-laptop/latitude_7490_om/diagnostic-led-behavior). I want to note that nothing ever gets displayed (no Dell logo).

I want to ask what else could possibly be causing this and how to fix it?

Solutions I've tried:
- Any possible RAM slot combinations. I've also cleaned up the slots themselves with brush and all.
- Removed CMOS and battery, tried everything again. 
- Built-in-Self-Test (BIST) works.
- I have not tried using other RAMs but I think my RAM isn't the problem when I'm getting a 2-5 when i should be getting a 2-3 pattern.

Unusual behaviors;
- I can't turn the laptop off through the power button. It auto restarts itself. I can only turn it off if I disconnect the battery and not on AC.
- Auto power on when I connect on AC.

I appreciate all the thoughts and help on this!