Has anyone stayed in a Erasmus internship for more than 3 months at FU Berlin?

Hi everyone,
I have a question specifically for international students who have done an Erasmus+ research internship in a research group or laboratory of Freie Universität of Berlin.
According to the FU regulations, is it possible to stay for longer than 3 months if your supervisor/research group agrees?
Has anyone here actually stayed longer than 3 months? If so, how did it work in practice and were there any administrative issues with FU?