Hi

Unfortunately this all does not really help. The proxy you use is nearly identical to the base mesh in all regions, so there the distance is 0 and it behaves exactly identical to the base mesh. So when distance is 0 makeclothes simply copies the vertex.

For the vagina the program looks for the nearest 3 vertices using mathematical functions, partly containing trigonometric functions and so it is just not 100% exact after a few steps of calculation. A vertex (-1,0,0) will not lead to the same result as the mirrored vertex (1,0,0). A tiny difference between left and right and vertex would try to follow at least one different vertex on one side. In rest-position this is of course not visible, because it is not deformed. But when you move the slider it becomes visible.

Workarounds:

You can use only 3 vertices as a reference to follow (a triangle in crotch area, one vertex left leg, one right leg and one in the middle to follow exactly these). But that will give strange results where the zones are connected to the rest.

I had exactly the same problem. When I export the character to blender I always have to recreate symmetry in Blender (even for non-proxies sometimes) but only for the body, not for clothes. But I need symmetry for different reasons because blender is no longer able to find the proper corresponding vertices for mirroring.

Finally I wrote a small blender plugin to create a symmetry table one time with the original proxy (or mesh). This symmetry table I can later use in Blender again to symmetrize same proxy as long as the vertex order does not change. Now the table helps to find the corresponding vertices. Since then I use this method for all, which was symmetric and should be symmetric after some changes, The table of the base mesh is used inside maketarget btw.

Software is here (you only need the stuff in folder blender2_8):

https://github.com/black-punkduck/MakeHuman-HelpersAnd a small tutorial here:

https://github.com/black-punkduck/MakeHuman-Helpers/wiki/blender279weightplugin.mdAnd inside MH? To conclude: the concept of MH will not really allow a 100% symmetry for proxies atm.

It could be achieved when the mesh loaded always would have a symmetry table like I did in the plugin. Atm. this information is lost for proxies. This symmetry table needs not only to know which vertex is left or right side and how to correspond, it also needs to know what is mid because these vertices must be pushed back to x=0 when symmetry is generated (or correspond to themselves which means the same of course). Not that easy to be implemented atm