Trying to copy and paste an image that has a mask

I'm trying to copy and paste this image which includes a mask (the cup part of the cupcake), but it's not pasting everything. Even weirder, when I un-select and re-select everything to try copying and pasting again, the result is not always the same. The first screenshot is the finished cupcake. Second is with everything selected. Third, fourth and fifth are different erroneous results from different attempts.