Gaming mouse with extra programmable buttons set to modifier keys (Shift, Alt or Ctrl) does not work consistently.
Same extra buttons assign to alpha-numeric characters do work.
This is true for both 2 Razer Naga Hex and 1 Hex v2 mice and Logitech G602 mouse.
This seems demonstrably to be an OS issue and can get no joy from Apple
I noted that when connecting each new mouse the OS (10.11.6) always notices the new mouse as an unrecognized keyboard and asks you to push the key to the right of the shift key. This, of course, does not work as the mouse is not a keyboard and has no hard programed shift key.
The really odd thing is that intermittently, the side button mouse keys assigned to modifier keys (shift, Alt + Ctrl) do work as they should and then after weeks of working properly will suddenly stop working for a time and then start working again for no discernible reason with no changes to the computer during that time.
I have bought 4 new mice in the passed 6 months assuming it was a problem with the mouse. Then I bought a mouse from a different manufacturer and had the exact same problem.
I have kept the mouse drivers up to date through all of this but have stopped updating Mac OS for the time being.
I need a solution, please