By the looks of the center where the sun hits it is a clue. Without checking the basement or crawl space(if there is one) which may contribute to the finish not drying properly is that they put a second coat of finish on before the first one dried. Very common issue.
CLOUDY FINISH What it is: The finish appears cloudy or milky. Cause: • Applying finish over a coat that isn’t dry enough to be recoated yet. • Applying waterborne finish during very high relative humidity or over a floor that is too cold to be coated. • Applying an oil/solvent-based finish during very high relative humidity, causing condensation on the surface of the drying coating. This will leave a dull appearing finish once the finish is dry, often referred to as “blushing.” Abrade/screen and recoat, being sure to increase the dry time between coats. Check with a damp rag before abrading/reapplying finish to make sure the cloudiness has disappeared..
You screen Parquet on a 45 degree .. hit it with a 60 grit , then a 80 ..