I have a UPS 15-55 SFC running in a residential hot water circulation system. The plumbing was drained for work and then refilled. When turning on the pump, three days after refill and air purge from the faucets, the grundfos seemed to work - I could hear water gurgling through and then (I thought) go quiet. After an hour of running, I found water was not circulating. I felt the housing of the pump and it was too hot to touch. I opened the nut and water came out - not air. There is also a small piece of white material floating in the water behind the nut. The shaft rotates freely. I cracked open the isolation valve and water also came from there - not air. The pump makes more noise than before, and I don’t think it is pumping. I am trying to figure out what happened (did I miss a recommissioning step), what is the status of the pump, and what needs to be done to fix it. Can you provide some thoughts and recommendations?