ZBrushCentral

Symmetry problem - points slightly off the z-center

I recently discovered a symmetry issue on one part of my model.
I went to subdiv 1 and moved around some verticles with the move brush in order to “unbug” the smart resym. I’ve used smart resym before so I know how to use it. Now the problem is not that the actual sides are asymmetrical but another: Some points that run exactly along the z-axis are slightly off-course and I have no idea how to properly put them exactly on the z-axis again.
I’ll upload an img so you understand what I mean.

Now you might say: oh but that’s noting - they are almost on the z-axis.
But the only reason they are is because I manually moved them there.
Now is there any way that I can place them back properly on the z-axis without having to use the move brush? And if it isn’t, then I wanna make sure that this kind of symmetry problem won’t do any damage later on when I UV-wrap in Roadkill. Also this small lack of symmetry becomes bigger at higher subdiv levels and I don’t wanna re-align hundreds of verticles at subdiv6

Also: using the smoth brush and “just resym” several times in a row doesnt seem to work either. After doing that followed by a smart resum (saying full symmetry found), this error appears again if I go to subdiv 2. Then if I go back to subdiv 1 it’s like I never even did a thing.

I managed to fix this by doing the following:
-move verticles
-smooth surface
-resym
-smart resym
-go up one subdivision
-redo the process