Oh crap ! I don't like the sounds of this either. I could see the house filter being missed while winterizing ,if pumping pink AF with/ through the pump but the pump would be fully winterized in like 2 seconds if isolated from fresh tank properly . Or if some large winterize pumping system used city hook up ,maybe pump get missed and frozen but both pump and filter seems like not winterized at all. Was there any pink AF coming out of lines at all. Hard to prove owners didn't hook up to water after winterized after CW did winterize. They will try to claim I'm sure. I hate to say this but freezing is not covered under warranty... maybe some insurance claim due to CW negligence. I hope all works out , just reading this hurt me.
You need to document what you find maybe call insurance now to 2nd party involved witness damage.
95 Monaco Crown Royale
M11 400hp, 4060 trans.
Aquahot, Generac Guardian7.5k