I tend to use Ctrl-C / Ctrl-V for copy/paste operations (Windows 7). However in ScoreCloud Studio, I frequently found (I first thought) that Ctrl-C/Ctrl-V appeared not to have taken any action when I attempted to copy a number of bars. I have found however that using the Edit menu top left of screen and selecting copy and paste from that menu, works consistently well.
I later realised that Ctrl-C/Ctrl-V had in fact copied the the said bars ON TO THE END of the whole composition, and not at the point selected for pasting. (This effect was not initially observed, as the end of the music was not currently on the screen).
This erroneous behaviour does not always happen, but certainly does quite often.