Adding a task to a different board copies the section of the original board to the other board

Hi @Martina_Pielka, welcome to the Asana Community Forum :wave:

I’d suggest reaching out to the Support team with the Project URLs and task URLs so that they can take a deeper look at this for you. As our Support team has access to additional tools that we don’t have here on the Community team, they can look into the backend of this for you.