question about the redact tool

Hello,

I have tried to use the redact tool in a new PDF ie :

Before that, I had made a collage from another PDF to this one : you can see here the collage : if I select the collage, it is surrounded by a blue line :

But then I have removed something in this PDF by using the redact tool. So the redact tool asks me to save in a new file, but when I open this new file, if I select the same collage, it does not select the selected collage, but it select all the page. Why ?

My goal would be, in the saved PDF (after the redact tool) to be able to select again the same collage only, like this :

Because, I need all the time to be able to change the position of each collage on the page.

How to be able to do that  in the saved PDF after the redact tool ??