Hi Fran @Makiton ,
Thanks for adding a screenshot!
That is indeed not Individual, but in two pieces as you say…my guess is, that it Insets that way, because the top and bottom part are really two pieces.
So before Insetting, select everything (A) and then M > Merge > By Distance. (For good measure follow it with SHIFT+N, to fix possible inconsistent Normals.)
