Hello. I have lived in this circa 1990, split floor plan house in FL for 23 years w/ no plumbing problems. Recently, slight amounts of grey water sporadically back up in the master tub. Timing is unknown—never actually see it happen, however the dirty evidence is there. Plumber has used camera down vent and thru all pipes. Pipes have been snaked and hydro-jetted. County Public Works has checked connection to sewer lines and says all is good. Plumber rechecked pipes w/ camera thru clean-out. All clean yet still sporadically backing up. Surveyed other houses in neighborhood w/ same floor plan. This is only house w/ issue. Plumber is flummoxed and giving up—says there is nothing else to do. Very frustrating… there must be a fix! Seeking your guidance…. Thanks, Chris