Two reports in a dispute, or a disagreement with your own manager. Don't let it resolve itself, it usually won't, and letting it sit signals that you'll let things sit.
The instinct to hope a conflict cools down on its own is understandable and almost always wrong. It usually just goes quiet on the surface while it keeps accumulating underneath, and it resurfaces later, bigger.
Two engineers keep clashing over code review comments, one reads them as blunt and dismissive, the other thinks they're just being thorough. Talk to each of them alone first. You'll likely find the real issue isn't the comments themselves, it's that neither has told the other how they'd prefer to receive that kind of feedback. Name that pattern, get their agreement on a specific fix, and check back in two weeks.