Its the rotating shaft the cable quadrant mounts to. It will ride up
just a skosh after a few rotations......weird
The seal on that shaft has nothing to do with the shaft "rising" on you,
You need to take a look at the end plate on that end of the pump. I'm wondering
if someone hasn't taken that end plate off and did not reinstall it properly.
Somebody may have replaced the seal on that end plate?
There is a 90 degree metal "tab" on the inside of that end plate - when you
install the end plate, you have to make sure that you push down on the cable cam
so that that tab "slides in" and "locks" the "camshaft" in its proper place.
That tab HAS to sit on the upper small part of the shaft and it is what prevents
the shaft from moving up/down. It is important that it be installed properly.
One "give away" if it is not installed properly is that the end plate will
"bulge out" and the cam will turn harder than it should.
I have seen some of those end plates where that metal tab has broken off and
that can cause some problems.
If I were you (or if anybody else has this same problem) - I would for sure
remove those 2 little screws on that end plate and see if that tab is still
there and is in the right place.
If the end plate is installed properly - that shaft should NOT move up/down and
the cam will turn easily.