When do feedback loops fail to work on an ecosystem?
if you could explain the answer, that would be awesome :

Feedback loop will fail in an ecosystem if the factors regulating the feedback mechanisms fail to function.

Explanation:

Feedback loop is the phenomena in which output is circled back in a way that it is used as input again i.e the reaction is circled back. Its a continuous process.

There are two types of feedback loops, positive and negative, one functions to reinforce and other functions to balance. Positive feedback loops enhance the outputs while negative lower the output and keeps the balance. the variables that are involved in all these processes effect each others so, by eliminating such variables or factors will cause failure of feedback loops.

me and my friend did 2

well, i believe that the answer is 2. : 3