Low airflow from only one vent may mean a closed damper, blocked register, or duct collapse
https://localhvacrepair572.raidersfanteamshop.com/frozen-ac-coil-florida-why-it-happens-and-what-to-do
Low airflow from only one vent may mean a closed damper, blocked register, or duct collapse. Check the vent first, then investigate deeper if the issue remains.