Same behavior here. Middle Mouse Button (button2) not working, starting
xev | grep button
try it multiple times; button event occurs; stop xev and the button keeps working.\
Environment:
KDE Neon (based on Ubuntu 18.04) with mainline kernel verion 5.1.2-050102-generic
Hardware:
Logitech USB-PS/2 Optical Mouse connected to a Lenovo Yoga X380 via Thunderbolt 3 Dock
Same behavior here. Middle Mouse Button (button2) not working, starting
xev | grep button
try it multiple times; button event occurs; stop xev and the button keeps working.\
Environment: generic
KDE Neon (based on Ubuntu 18.04) with mainline kernel verion 5.1.2-050102-
Hardware:
Logitech USB-PS/2 Optical Mouse connected to a Lenovo Yoga X380 via Thunderbolt 3 Dock