In UMG, copy/pasting a button where the child of the button is named one of many characters ("<" for example) will cause the button to paste empty, however I am unable to add anything to this button and pasting something in causes UMG to crash.
You can reproduce this easily by creating a new project, creating a UMG widget, make a button, add a child to the button such as text, now name the text “>” (without the quotes), now copy/paste the button, you will see that the button has successfuly pasted but it is now empty, I am unable to add any children to this button and pasting anything into it causes the editor to crash.
I guess it has something to do with core copy/paste functionality. It’s done via text buffer where objects are incapsulated in <> (Begin Object and End Object) so perhaps this symbol creates a conflict somehow, when it tries to parse its Name property.
I guessed it would be caused by that, and I know it’s bad practice to use spaces or characters in internal variable names but either the characters shouldn’t be allowed or the issue should be fixed as it could cause some confusion as to “why has my editor just crashed?” or “why can’t I add stuff to my button?”
Of everything in Unreal Engine 4.7 right now I’d have to say that UMG is probably the least stable although it does work!
I was able to reproduce this issue on our end. I have written up a report ( UE-11213) and I have submitted it to the developers for further consideration. I will provide updates with any pertinent information as it becomes available. Thank you for your time and information.