A headscratcher. Keyboard problem

[letmewearurskin]

So sometime last year, I borrowed my laptop to my sister, 3 days later when I got it back, it worked fine for about 10 minutes and then keyboard just went haywire.
First, it started randomly capitalising letters. For example if I needed lowercase b I had to hold shift and press b for it to be lowercase, even if caps lock was off, and if the caps lock was on it would be lowercase b, but every other letter that wasn't f*cked would be uppercase.
So, I tried to update keyboard drivers, disable them etc. Didn't work, so I wipped my hard drive, installed  windows, from a clean install. And it worked for a few months.
Then it happened again. Out of nowhere. But it was worse this time. Number row above the letters wouldn't type numbers, just the symbols. Even if I hold shift or any other similar button. And then sticky keys would go nuts, even if nothing was touching the keyboard or the touchpad. I cleaned it. Took off every cap washed it and put it back.
Then I installed Linux (popOS) thinking maybe windows at that update was messed up for my device(which happened before with wifi) and I used linux for a few months. And then it happened on linux as well. Number row and random uppercase letters.
So I knew there was a new version of windows (20H1) so I reinstalled windows. It was fine up until after New Years Eve. And then it happened again. But this time it was even worse. Bc now even my numpad  stopped working. I couldn't even log in. I was so frustrated. Other people have similar problems, but aside from getting a new keyboard(which I haven't), none of  their fixes worked for me. So, to refrain from throwing the laptop from 4th story window. I just shut it down. And left it.
Last night I turned it on after 4 months for the first time. And it worked. Keyboard worked perfectly. I shut it down and went to bed. And today when turned on it worked normally. Then after about 2 hours. I noticed This PC icon highlighted. I always deselect everything, when i'm stepping away. So I pressed an arrow key and it selected every icon in first two rows on screen. Also on screen keyboard has the same problem as my actual keyboard. And keyboard checker says all buttons work fine. Most of the time. Sometimes ctrl shift and alt would be gone, but if you press another letter they would come back.
And the thing is it's not like it just doesn't work correctly. It's that it works, and then it just doesn't. And then it works again.
Now, I'm at my wits end of what to do aside from buying a new keyboard. And I didn't do it up until now cause it's expensive, even used one, for where I live. The same reason why I still have 4GB ram instead of 8, it's one slot board. Despite having it for 4 years. So I'd like not to buy a another if possible.
The laptop is Lenovo Ideapad 100-15IBD type80QQ.

[kelvinhall05]

Well it's pretty obviously a hardware problem and you can't really disassemble and even try to fix laptop keyboards, never mind doing it successfully. Replacing the keyboard is your only option.

[letmewearurskin]

12 minutes ago, kelvinhall05 said:

Well it's pretty obviously a hardware problem and you can't really disassemble and even try to fix laptop keyboards, never mind doing it successfully. Replacing the keyboard is your only option.

Yeah, I figured. But as I said it's expensive, so I wanted to be sure it's the only option before I commit to buying one. Thank you tho.

[kelvinhall05]

5 minutes ago, letmewearurskin said:

Yeah, I figured. But as I said it's expensive, so I wanted to be sure it's the only option before I commit to buying one. Thank you tho.

And I understand it's expensive. But seriously, it's your only option. I'm guessing your sister spilled something on it or set something very heavy on the keyboard (water damage is more likely imo) and the only way to fix it would be to take it apart to the point where you can access both membranes and clean them, then reassemble and hope everything works. It's likely rivited shut and impossible to open, and reassembling would also suck.

[letmewearurskin]

Got a replacement keyboard, installed it and everything works great.

But the night before I got the replacement, I wanted to watch a tv show and the buttons were driving me crazy, I couldn't read the subtitles.

So I opened the onscreen keyboard app, and turned off every key I could, caps, numb lock, ect. And shift keys just kept going crazy. So I took the caps off. And it stopped.

Right shift just doesn't work, left one goes crazy with littlest pressure. So, it's the switch(or however it's called) that broke. Because the lines(wires) are still under the tape and it's completely sealed. (And my sister said she was extremely careful around the laptop with liquids and handling it, cause I would have murdered her otherwise (which is absolutely true).

So you were right, not worth fixing the faulty keyboard. And the headache and the hassle it would bring.

I just wanted to be sure it was a hardware issue and know what exactly was broken. Now I know, and have extra caps, in case I vacuum some again, and forget to fish them out. So I'm extremely thankful for your help!