Low airflow from only one vent may mean a closed damper, blocked register, or duct collapse

https://trustedsamedayac465.rivetgarden.com/posts/low-refrigerant-ac-problems-signs-your-system-needs-attention

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.