My guess is that one of the pauses isn't long enough in the macro. When something gets copied to the clipboard, there's no way to tell when it actually finishes getting copied.
So if it happens again, my guess would be that the last Pause action isn't long enough. It's right before the "Paste" action, right near the bottom before the "Cleanup Variables" group:
It's at .4 seconds, so you could try increasing it to .6, or higher, and see if that helps.
If you end up doing this and it solves your problem, I'd appreciate it if you posted here to let me know.
Thanks!