If I were to use a command block and lets say change my gamemode in a certain area, for an example, /gamemode adventure @p x=#, y=#, z=#, dx=#, dy=#, dz=#

and were to see if it works in that specific area it would not work, and it would sometimes work in the wrong area so it would say "no selected target matched" I have tested this several times and it is not a human error. 

I hope you see this, thanks.