This is a bug, Kevin. Sorry about that! It’s already fixed ahead of the next minor update, but for the time being you’ll need to employ a workaround. Use O to engage Force Durations, use , to engage rest input, then set the duration to quarter and input a rest (e.g. type Y) at the start of those bars, then use Remove Rests to remove the redundant remaining quarter and half rests that will appear in the beats occupied by the slash region.