Using Poser Pro 2012, similar to P9 and I can not seem to cause it do what you are seeing.  I have used ctrl C and Crtl V to copy multiple frames across the time line.  I can collapse the pallete down to just Andy and copy a frame with no problem.  Selecting multiple parts when expanded allows me to copy them a different location as long as the parts that are to be pasted too are selected with the white outline.  If the copied part is larger then the destination then the parts not selected in the destination will not be pasted.  You can select more parts in the destination then in the source and only the parts that match in both will get the keyframe applied.

The only time I get something like you describe is if I copy a single part like the shoulder and paste it to a single part like the forearm.  But that only occurs if it is a single part to single part, and the manuel warns against doing that.  If either the source or destination is multi-parts then it will not paste unless they have overlap.

Poser 5, 6, 7, 8, Poser Pro 9 (2012), 10 (2014), 11, 12, 13