I re-assembled a T60 last night and replaced a display panel since it was cracked.

Since then, I've noticed that it isn't as strong as it should be, even though I followed the Lenovo hardware guide.

Here's a video comparing two nearly identical T60s with each other. (Sorry about recording it vertically) The one I'm referring to is on the right. It warps much easier than the one on the left, which is manufacturer assembled.

I did leave out these: which I don't know where they go since they aren't listed on the guide, but could they possibly have an impact on what's happening?

What kind of screen did you install? normally squeezing the bezel won't put pressure on the LCD like that, the Lenovo LCD (the ones I've seen) all have a metal frame that protects the screen and the bezel had some mild adhesive that holds it onto the frame. If you got a generic screen, then there is probably nothing you can do about it short of returning the screen and getting a genuine one.

It's a Genuine Lenovo screen pulled from a donor T60. It had a metal frame and the adhesive that holds onto the bezel.