I have forever used some combination of ctrl--alt-shift-drag to copy and constrain elements. Even though the alt key is not technically required, it has never been a problem until now.
Now every time I try to drag copy and constrain an element, it looks like it's going to work then just disappears. If you don't want to support alt in the mix, don't preview the drag copy event. It is completely senseless to let someone struggle to do it the way they have always done it and then just not do it. Stop previewing it if you rerfuse to support it. But better yet, just ignore the alt key--let it be pressed or not pressed when dragging and constraining a copy.
And AGAIN, these topics do not apply in any way. So I am giving people misinformation by selecting one of your topics below--since I have to to submit this bug. Please fix the tag thing. I am going to post this with every bug report and I suggest that others do the same.