Getting background when trying to remove with generative ai

Hi, all!

I'm desperately trying to remove some elements using the generative ai in Lightroom CC on mac, but all my attempts gives me a slightly faded shadow where the element used to be. This happens no matter what I try to remove. What am I doing wrong, or is it something to do with my settings? I have attached three files to show what I mean. File3 is the original. File 1 is my attempt. File2 is made by my colleague on her mac, exactly the same way as I did, but it is this I want. Another colleague (on Windows) gets the same result as her. What is happening, and how do I fix this?