Still having this issue...
It sounds like either something isn't being copied over fully, or it's conflicting with something in your existing project maybe. Try turning off any plugins and other events one by one and narrow down what could be causing it to lag.
The Relationship System template also uses corescript 1.9.0, which probably won't affect anything since the events should all be the same, but maybe try making a backup of your project and updating the corescript files.