Stop in for a cup of coffee

So I went over to grab a new shut off valve for the outside water line.
Every year I shut it down and drain it. Every year the copper line would splint. It's an empty line. So last spring I pulled everything and went to pex. Turning the water on and the pex line on the valve pops off. It was fine since around this time last year. Till I shut off the water and drained the system. I give up.