lipsync

Hi guys, I have a problem with my MOUTH LAYER in Animate, I have the mouth on a single position about 5 minutes, I make the lip sync btw with an audio layer, after 5 minutes I want to change the position of the mouth, to put on another character for example, but I make a new keyframe but just in that keyframe the mouth change her position, because next keyframes are maked by lip sync, I tried to copy the new position of the mouth keyframe and paste manually on each keyframe maked with lip sync, to have the new position on all keyframes that are already maked with the lyp sync... I tried too to copy the keyframe and paster over all next keyframes and frames but doesn't work. Is a solution to make in one step this postion change of an mouth layer to overwrite to the already lip sync keyframes ? thank you...