This is the same basic problem as you’re discussing in this thread: even though it’s obvious to you and me, Dorico doesn’t know that “mute” and “mute off” (which send the playing techniques “mute” and “open” respectively) are opposites, so it doesn’t know that it needs to switch off “mute” in order to switch on “open” – instead, it ends up looking for “mute+open”, which is nonsensical. Dorico needs to be taught about which playing techniques are opposites of each other, or at least which ones are mutually exclusive with each other (consider a group like arco, pizz., left-hand pizz., col legno, tremolo, con sord., senza sord. etc. and how some of them can be combined – e.g. pizz. and con sord. – and some cannot – e.g. pizz. and col legno). This is something that we will do as soon as we can, but until then you will find that you need to employ a “nat.” or “ord.” before practically any change of technique to get a halfway sensible result. Obviously we do not consider this an ideal state of affairs, but it requires time and effort to improve it.