MacBook Pro - Intermittent partial keyboard failure

Hello, I'm new here, thanks in advance for any help.

I have a MacBook Pro that's just out of warranty. Sometimes a large portion of the keyboard will stop responding, although the top two rows are always functional. I took this to mean the keyboard was bad and replaced it, although sadly, the problem remains. Sometimes if I push down on the top case, the keyboard will work properly again, although attempting to move the ribbon cable or connector directly doesn't seem to make a difference.

I'm assuming that it has to be either the ribbon cable, or the small board it plugs into, directly under the trackpad.

I'm wondering if anyone has seen this problem before? Any recommendations? I don't really have spare parts around to test with, so I have to order and try. Should I start with the ribbon cable first?

Any insight greatly appreciated. Thanks much!

--Jeremy