Use all F1, F2, etc. keys as standard function keys not working
I had the same issue but found a solution. You can enable/disable the feature by pressing the fn+Esc keys on the LMP keyboard. Apparently it's a feature built in the firmware and can't be adjusted with software. It took me hours to find out...  

I tried everything first. I downloaded Fluor, Karabiner, FunctionFlip, nothing worked. Until I found that little leaflet in the box with instructions...