Still hot air 2nd floor stairwell summer and winter

I have 2 bedrooms on the 2nd floor both with returns in the ceiling. But the 1st floor unit is pushing the hot air into this stair well. It’s not my largest complaint but if there’s an easy fix I’m all for it.

Also during the summer the stairwell gets really muggy and humid while the bedrooms are fine. I feel like I should add a return to the stairwell ceiling.

Any advice would be appreciated cause I would love to get my system dialed in already. Thanks

source https://hvac-talk.com/vbb/threads/2235669-Still-hot-air-2nd-floor-stairwell-summer-and-winter?goto=newpost