U150 keyboard malfunction after changing screen, = repeating, few numbers not working

Question

Hi!
I changed my cracked U150 screen on my own (warranty is passed).  I thought it worked fine on test boot before attaching the bezel.  I aborted the test boot (as the instruction video said to do), and put on the bezel with some difficulty (it's a tight fit on the bottom of the screen around the hinges).
The next boot up failed, which I've never seen before. Got a bit worried, as it wanted me to try recovering to a set point (several weeks prior).  Opted to just turn off and back on, and it seemed to work...EXCEPT now a few keys on the keyboard malfunction.  Esc, `, 5, 6, 0, ) and Delete all type their character and then immediately type an = which repeats.  The actual = button does nothing: types nothing.  In caps, the keys do the same thing, but of course type a + which repeats.  F5 also does it, and I'm not sure about other F keys because I don't want to do some function that will shut down my typing right now! 
U15============ 0========= )+===========  When I press any other key, the repeating equals stops, of course...
When I boot up, the computer beeps repeatedly as if a key is repeating in error, so something in startup must use one of those keys and causes the same issue: since I don't actually press any key on bootup, does that indicate it's more of a software problem than a hardware problem?
I've taken off the screen bezel again (a real pain and not a good repeated activity because I typically break one tiny plastic clip each time no matter how careful I am) and no change. I see no keyboard cable anywhere near the screen or cover or hinges-just WLAN cables and the camera. I did not spill anything on the keyboard and it worked totally fine until I replaced the screen. Online info about Lenovo S or Y series seems to show the keyboard cable down low, so again, not near the screen.  The screen website (laptopscreen.com) folks had nothing to say that helped. My search online shows nobody with a similar experience. 
There is no Lenovo keyboard driver on the Lenovo site, so I don't see that uninstalling and reinstalling the driver would make a difference: besides, how do I reinstall a keyboard driver if I can't use the keyboard once I've uninstalled it?  Is the mousepad enough to reinstall?
So, I would be ever ever so grateful for any help/ideas. What's my next step: taking out the keyboard to see if the cable loosened, even though I went nowhere near the cable??
Thanks!!

Answer 1

So it's been a while, but these things can drag out in life...now my brain is starting to adapt to the change, and that's annoying, so I'm back at trying to fix this.
I tried safe mode, and the problem persists.  I tried returning all my startup options to default, and it persists.  I previously had returned to a Restore Point before the problem, and that didn't fix it. 
Today I was going to look at the keyboard cable, but getting the top off is proving to be difficult and since I can use the machine as is, even if annoying, I don't want to go there yet.  Besides, there is no reason for this to be a hardware issue:
I aborted a bootup by pressing and holding the power button.
Next bootup failed, and the machine asked me to restore to a previous Restore Point.
I turned off the machine again instead of restoring, and ever since then I've had the keyboard problem. 
I tried uninstalling the keyboard and restarting computer so the driver reinstalls, and that didn't fix it.
I plugged in an external keyboard and that worked fine.
I am now wondering about using Linux to get at the problem.
Any ideas?  I totally appreciate how active you are on this forum, and all the folks you've given advice to.  You are making computers work for people: thanks!!
Tamarinda