How are you getting anti-freeze into your water system? I wonder if your suppply is low. I have experienced strange behavior when the water level in the fresh water tank is very low.
When I winterize my trailer I first drain the fresh water tank and water heater. I then pour 8 or 9 gallons of non-toxic RV anti freeze into my fresh water tank. I then run the hot water at the kitchen sink until strong (not diluted with water) anti-freeze comes out - about 6 gallons. I then run the cold water at the kitchen sink until anti-freeze comes out. Next I move to the pressurized city water inlet, toilet, and finish with the shower's hot and cold lines. When I am finished, a gallon or two of anti freeze remain in the fresh water tank. There is also a bit of anti-freeze left in the black and gray water tanks.
It may help to study the schematic diagram of the plumbing system found in the owners manual. Don't have one? Read the one that came with my Scamp
; I have it posted on my web site - URL listed below.
-- Dan Meyer