My trackpad has become stiffer...
I can't imagine that being a software issue. Trackpads are surprisingly precision installed. I remember it taking me awhile to get the hang of a trackpad replacement. The tolerance on them is the width of a piece of paper on both ends of all four sides. I used 8 small slips of paper to hold the trackpad perfectly centered before doing the final tightening down of the spring strips along the top.
If your trackpad is stiff, you might try taking a thin piece of clean stiff white paper (printer grade) and running a corner down into the gap and dragging it around the perimeter, to clear out anything that's stuck in the gap. It's easy to get a bit of dirt or a (small!) grain of sand etc in there. The trackpad is attached at the top toward the left and right sides so you won't be able to clean that as well or as easily, but thats the hinge of the system so debris in that gap is usually less of an issue. The button that clicks when you press down is in the bottom center of the trackpad.
If your trackpad isn't sitting level, like you can feel it raised in the lower left and lowered in the lower right, you will need to get it adjusted at an apple store etc. They may need to replace the spring strips. If it's not level, that's a pretty good indicator you're going to have problems clicking it.
The click depth of the button is also adjustable, and has to be carefully set for proper depth, to not hold any pressure on the button when up and yet not have any gap. (these buttons can also wear out, necessitating a replacement trackpad) They're lock-tite'd into place but can require adjustment on rare occasion.
BTW in case you didn't know, the trackpad is made of GLASS. I've replaced a few that were damaged by objects being dropped on the top deck. They shatter but stay together due to all the electrical magic underneath. I've also seen a number of them with a crack. Strangely, in most cases they remain usable in this state. But they're surprisingly tough.
