As requested by developer on blender bugs I opened this thread.
On blender bugs I was reporting the grab brush, but the grab brush is working. I just needed to apply the subsuface modifier. Now My quest is, when I select vertices blender automatically deselects them. But this depends on the distance from the vertice.
Disclaimer: I m not a developer, I m just a user who has been using Blender for sometimes now specially sculpting.
About your vertices problem can explain more or make a short video for me to see what you are doing. I tested your model again, box selection is working just as intended.
One way diagnose the problem is to load factoring settings and try if Blender is still behaving strangely.
I don’t know what the problem was, but I would select the vertices and it would deselect them. I then had to zoom away and it would work. Now I cannot reproduce the bug. When I was editing, I was editing a subsurface cube. If the bug shows again I’ll try and catch the blend file.