Chemical reaction between the oil based stain and the water based polyurethanes. The quarter sawn flooring is vertical grain, and the stains seem to take longer to dry as opposed to plain sawn flooring. You did not list a time frame for all the finishes and drying times. They could have poured the stain out in that spot and worked out it making that spot heavier; or if they ragged the stain on that could have been a spot where the dipped the rag in the stain and worked out of a "puddle" there. Both would cause a heavier concentration in that area.
I would suggest using a dri fast natural stain (dura seal) Bona Amber seal as your sealer, then abrade and top coat with the traffic. We install a lot of quarter sawn flooring, and this is the process we use and do not have any problems with it. *knocks on wood*
I would suggest using a dri fast natural stain (dura seal) Bona Amber seal as your sealer, then abrade and top coat with the traffic. We install a lot of quarter sawn flooring, and this is the process we use and do not have any problems with it. *knocks on wood*