When you give yourself a player head with your profile, it has the skin you are wearing. When you leave, change your skin, and rejoin, all player heads with your profile previously given or placed, change into the new/current skin. In past versions such as 1.21.8 this is not so, the player heads placed or in your inventory keep the skin they originally had.
Mannequins also act this way which may be intentional.
I’m aware that this change might not be a bug, but I’m worried at the damage this might cause in some of my worlds where I use player heads with my profile as specific skins, and I don’t want that data to be lost.
This is intended per the changes in the 25w34a changelog.
You can use
/fetchprofileto create a static head/mannequin as opposed to a dynamic one.Existing heads should remain static if they were before.