I seem to remember mine has stuck on a couple occasions, but I don't think during the winter. I too put the pink stuff in the bowl.
However, when it has stuck has been in the summer after the first trip and before winterizing. Since it usually only gets one or two trips per year, flushing out well after each trip is essential. Since the water gets shut off to the coach (because I don't have a splitter and have to use the one spigot), the wand goes down with no water coming in through the toilet. When done, if the wand isn't turned back on to put a little water in the bowl, the valve closes dry.
2007 T-286SR Cherry/Granola, #6236, original owner, current mileage: 9467.8 (as of 5/26/19)
1997 T-2653 Blue Denim, #5471
1979 12 1/2' MC, Beige & Avocado, #4639
Past Sunlines: '97 T-2653 #5089, '94 T-2251, '86 T-1550, '94 T-2363, '98 T-270SR