Heater issues. Some vents blow hot air, but middle blows cold air.

What is your question?

Why does my heater not work through all vents? The vents on the outside near the door blow hot air when heater is on, but the 2 in the middle blow cold air. May be unrelated but there was also a lot of hot air coming from the 2nd row seat middle area where the arm rest folds down. Could a vent be blocked at that point?

What makes this problem better or worse?

better when going over 80 mph (speeding)

How long has your 2014 Dodge Journey had this problem?

about a month