(example: 2.79b release)
(example: 2.80, edbf15d3c044, blender2.8, 2018-11-28, as found on the splash screen)
Short description of error
Select second vertex results selected more than 2 vertices.
Exact steps for others to reproduce the error
I select a vertex by click, select second vertex by click with ctrl, I have more than 2 vertices selected. This works like this only for some vertices. When I select by drag region (shortcut B), I can select only 2 vertices.