Generally, it's a bad idea to continue using Default after the initial install. It's meant to prove that a fresh install works, by grabbing whatever you're already using at the moment, but beyond that, it becomes a liability because it continues to follow the operating system's choice of device. So it may suddenly not work anymore, because Windows decided to use something else, and OBS follows it to also look at that something else.
Set everything to a specific device, never Default, and it'll keep working with that device, even when Windows decides to switch.
Back to the feedback loop, there are several ways to break it: just disconnect at one of several points like you did, or connect to different devices, etc. It doesn't matter how you break the loop, just as long as you do, somehow.
