My colleagues and I have been experiencing these same issues starting about 2-months ago. Any time we attempt to cut/copy/duplicate an object (text, shape, image, etc.) on a slide Storyline locks up. I'm able to copy/paste object names from the timeline, duplicate slides, etc. without any issue...it's only when we try to cut/copy/duplicate a slide object.
Every so often though, the problems will magically disappear. I say magically because we didn't knowingly do anything that would fix the problem. And, unfortunately, the problems always come back. I'm also afraid the issue may expand. Yesterday I was adjusting the corner radius on a rounded rectangle and that seems to have frozen the program.
My team has been using Articulate for about a year now and everyone likes it alot, but this problem is a deal-breaker. It's taking me at least twice as long to build a course file since I have to rebuild recurring objects instead of just copying them. If this problem doesn't get fixed soon, my recommendation to my boss is going to be to drop our licenses and go back to Captivate.