RW 5 and 6, Stacks 2.7.2. Yosemite.
I am unable to move or duplicate stacks on a page in existing sites or a new project.
Locked button is off.
I can modify text, replace images etc. Click and drag does not work.
Answer: Turns out I had updated my Wacom tablet/mouse driver with the wrong driver,
which caused the issue.
Reverting fixed it.