there are a couple of workarounds to the mute group, which are not great but easier occasionally. this is for the 2kclassic, don't know if they're the same for the XL.
1. Make all the chopped samples NOTE OFF and then play them as you wanted to - this works around the muting but you have to hold the pads for the chop's length and you can't repeat a note/sample easily (unless you double it onto another pad)
2. Doesn't work all the time but - Go into program mode, select the pad which has your non-chopped sample, highlight the filter section and hit open window. Switch the values on the bottom two options (can't recall them exactly, but one will be 0 and the other 100, switch them) Then go to main screen, hit 16 levels on the non-chopped sample (i.e. loop or whatever - forgot to mention this only works on samples that are measured or can loop) and select velocity. Then you will have your sample "chopped" onto 16 pads, but it doesn't really do it accurately. Actually if you have a sample that isn't a loop, you can get some interesting results. Especially if the sample doesn't have drums in it.