So, I finally got around to this. I bought a repack seal kit.

When I was taking this apart, I removed the checkvalve at the bottom of the rod. I'm not that experienced, by the way.

I had an idea of what it was and saw the spring inside. When I used a screwdriver to push the valve down, it was very hard to push and then gateway and opened. Now it moves freely with little effort.

Am I safe to assume it was likely stuck and caused this issue? If so, do you think it is fine to put it back and and resume operation? Or, does it need to be replaced for good measure?