To shore up your pipeline in 3dsmax, try installing this .OBJ exporter.
http://www.guruware.at/main/index.html
It does not appear reorder the verts as the native 3dsmax one does, which means a lot of problems with sculpting morphs, reloading UVS and so forth magically go away.
It also has a nice interface, and allows you to save presets for mudbox, zbrush and so forth. Very handy.
So the settings that seem to work well are…
Precision: 6 (A MUST)
turn OFF all optimise checkboxes
turn OFF flip yz axis. (you can turn this ON in export/import in Z-brush)
Hats off to the creator. It seems to have fixed my headaches this week!