I could have sworn...
that my legendary Entei changed when I went back into catch it. Has anyone noticed this? Would be interesting if in fact you could change the IV of your mon just by leaving and coming back.
My pokedex was full and when it first came up after the raid battle I was happy that it was 1890 something, then when I got rid of a mon to make room, came back into catch it, it was only 1860something. It happened one other time to me before, but it was a display issue, so after I caught it, it was the original CP after all but this time it changed to a junk 76%.
Answers
It is a visual glitch. If you leave and come back, its CP on the catch screen will change, but when you catch it, it will be what you encountered the first time. (The changed visual CP is actually one of the CP values for one of the other players that fought the raid in your group.)
Having your pokemon collection full and being unable to go to the catch screen from the beginning might be triggering this.
