If I move a unit back to a battlefield where I already scored a point this turn (using Ride the Wind), does a showdown occur even though it's no longer open for scoring?

Ruling: Yes, a showdown still occurs. When you move a unit to an open battlefield (one where you don't have control), a non-combat showdown happens with the normal opportunity for Actions and Reactions, even if you already scored that battlefield earlier in the turn.

Nuances:

• You will not score the battlefield again when the showdown resolves, since you already scored it once this turn
• The battlefield is considered "open" because you lost control of it after moving away