I ran a container of liquid plumber into the kitchen sink and let it sit for 15 minutes, then added approximately 10 to 15 gallons of hot water. I let that sit for an hour and pulled the galley drain valve, the water started slowly as in the past but then a massive blob of crap came through. The galley tank now drains normally like the other tanks.
I suspect the previous owner used the kitchen sink to dispense with all manner of liquids, bacon grease, etc.
All is as it should be other than the tank level read out which still indicates full. That’s another project.
2014 Dynamax Trilogy 3850 RL