Hi. I am experiencing much the same problem in my up-to-date build selecting vertexes in sketches so I came upon this thread.
I guess this is still a problem or am I doing something wrong?
OS: Debian GNU/Linux buster/sid
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.15864 (Git)
Build type: Unknown
Python version: 3.7.2+
Qt version: 5.11.3
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: English/UnitedStates (en_US)