A question often asked is "why when I press buttons to fire at a quick pace, why do some cues not fire?"
This is because the 18R Controller takes approximately 1 second to fire a cue on devices with A Hardware, and 0.4 seconds on devices with B Hardware during which time, the 18R will not respond to any further cues firing. After this brief period, you can continue pressing cue buttons to fire.
In general, 18R controllers purchased before April 2017 will have A hardware, and those obtained after will have B hardware. For more information on hardware versions, see Hardware Hammered Out.