Midi parts "linked"?

I’ve been working on some midi parts (bass and drums) and after I copy a few sections the two parts (on separate tracks) are linked, that is, when I select a bass part (not a track), the drum part is selected as well ( also both tracks become selected) and I can’t stop this from happening. I’m praying this is another goofy new “feature” and not a bug. Any ideas how to stop this from happening?

Has no one else experienced this? It’s driving me crazy…