Inspiron 15 7567, keyboard functionality after replacements

Hi,

So there's a bit of story behind this one. 2018 I bought my first laptop brand new, the inspiron 7000. Approximately 1 year and 1 week after purchase, when my 1 year warranty had failed, I spilt a drink on the laptop. The laptop died. It would make a boot noise, but black screen etc. Techs advised a replacement motherboard could fix it but no guarantee, at the time they were approximately 1/3 of the cost of the laptop, so I cut my losses.

2 years later, having been building and using tower PCs for years by this stage, I held onto the laptop with the intent to gut it and learn about how laptops function compared to a tower.

Therein, I pulled it all apart, started isolating all the units and finding out what went wrong. By this stage the cost of a motherboard replacement was only a couple hundred dollars as opposed to $600+. I had the motherboard replaced, and the system came back to life! HOORAAH. 

The hard drive, SSD & battery were fried. I removed HDD, replaced SSD, installed windows and was up and running again. Albeit with no battery.

HOWEVER, the keyboard was not functioning correctly. All the keys were lit up, but the "123asdzxc" weren't functioning correctly. With constant pressing, holding etc, the keys would work occasionally (with double/triple presses etc). However it was clear they were pretty shagged.

At this stage, I checked how to remove the keyboard / replace the keyboard, and decided it was out of my capabilities. So the laptop went back into storage.

A few years later again, with more knowledge under the belt, I decided to break all the rivets, pull the keyboard out and replace myself.

After completing the installation, now the keys that previously worked with difficulty (long holding, firm pressing etc) wouldn't work at all. The rest of the keys function fine, just the left side.

I've read just about EVERY keyboard solution on the internet for the dell keyboard, run every possible diagnostic other than one. I read in one article, the replacement of the motherboard could mean BIOS needs to be updated for this to work. I personally don't believe thats the issue based on the fact BIOS is the 2018 stock bios that worked fine previously. But as im holding onto strings at this stage, with nothing else working, my hope has been updating BIOS to have an effect. However, the BIOS cannot be updated without a functioning battery.

Today I spent $70 reluctantly on one last ditch effort to get this laptop function again, and ordered a new battery. This will at least enable me to use the laptop as a laptop, with onscreen keyboard if needed.

NOTE: Peripherals work fine.

If anyone, given what I've said has any solution on to what could aid in fixing the keyboard considering this:

1. Motherboard has been replaced

2. Keyboard has been replaced

3. SSD/HDD has been replaced

4. Battery is being replaced.

The ram seems to be functioning fine (1 stick of 16gb).

Is there any other component that could be causing this? I can't believe its taken 5 years for me to join dell support and post about this HAHAHA.

Thanks in advance, hope that's clear enough.