I thought that was how it was supposed to work. Press DRUM+MUTE+PAD to mute or unmute that pad, press only MUTE to mute/unmute the entire sequence and doing the latter with muted pads will unmute them all at once. I'm sure that is how it was supposed to be implemented? It works great for manually breaking-down a pattern then dropping it back in all at once. Individually unmuting each pad would not allow that.
Never had a drum pad not mute properly, but have a few time I've not really pressed the mute button properly. I now make sure I can see the muted pads showing before I mute another.
I use one pad track to run a drummachine, so I use the individual drum mute function all the time to kill and cue it's trigger. To mispress the buttons when muting/unmuting it is disastrous.