Keyboard intermittently not working
So I just bought a used 2015 13" MacBook Pro retina (A1507) for a Christmas gift. Checked it out with the seller for almost 20min and it seemed to be flawless. Got it home, reinstalled MacOS, still working. After about 4 hours working on it the keyboard started to act up. Sure enough it's now not working 90% of the time. Every so often after I restart the computer it will come back to life for 1-10min, but this is not consistent and mostly doesn't work.
All that's said the track pad is working fine, no issues at all.
Reinstalled MacOS - same issue
Put it in the fridge to check battery swell - same issue
Removed bottom case again for battery swell - same issue
Power button works fine
Keyboard backlight works fine
Trackpad works fine (which I find very odd since I've read they both usually go together)
I'd like to try and fix it myself, I've done MacBook fixed in the past and I'm confident I can do it from what I have read..... albeit slowly
I could replace the lower case but I'm not really interesting in spending more that I already paid. I'm ok with replacing the 100 keyboard screws and going through the process..... what else are holidays for.
Is there anyway to tell if it's the logic board or the keyboard, or both?
Since it's just the keyboard not working and not keyboard and track pad, I'm learning toward just the keyboard - is this a fair assumption?
Does anyone have any good step by step links aside from the one on iFix it? I like to have two for reference just in case.
Any other suggestions on the process would be appreciated!! I'll post my step by step when I get dirty.
Is this a good question?