Wood floors can expand and contract with changes in humidity- do you have central hvac and built in humidity control? As to swaying movement- hard to tell on the internet. Unfortunately most houses are built to the code minimum...

Thank you. I do have central air. i expected some expansions and contracting however didnt think it would create gaps.

I would bet you have I-joists throughout. And probably a kitchen island? The 3rd floor swaying would have to see video to understand your interpretation of that word.

The ”sway” is while laying on the bed I coulf feel the movement/motion. Also see me plants move.

Rhe kitchen is in a U shape not a stand alone island.

Might be some advice here.

https://www.houzz.com/discussions/5818579/2nd-floor-washer-dryer-low-vibration#n=10