When I copy a structure a random part of it is missing when pasting in.
I can't undo, says that I need to paste something first.
Tried updating the plugin, renew the config file. Didn't help.

If I paste in an old structure it's working fine also undo function.

Please fix it :) We need it

Good news! 
You don't even have to find out what's wrong. 
If there are no Xmas light (those connected to electricity) it all works. 
Copy and paste is fine and the undo also works. 
All you need to do is bugfix ;)