Answer:
The unpleasant episode can be seen in the third chapter of the text where Grete was playing her violin and the boarders as well as her family were around, listening.
Step-by-step explanation:
Franz Kafka's science fictional novella "Metamorphosis" tells the story of how the character Gregor Samsa's transformation into a bug had sent his life in turmoil. The bug became a menace to his family and even ruined their family's income source, leading them to finally move some place else.
The scene where Gregor had ruined his family's prospects was in Chapter III where he had been seen by the boarders. In order to maintain their family sustenance, they had given one of the rooms for boarding and it had been occupied by three gentlemen for sometime now. One day, while Grete was playing the violin, the music drew Gregor to it and he went nearer. But the boarders saw the disgusting creature and threatened to leave immediately. Not only that, they even told Gregor's father that due to the deplorable and odorous situation of the place, they will not be paying even for the previous days' stay.
This scene not only left them with no income but it was also the scene where the whole family decided it's time to get rid of Gregor, for he is a bug and not their son Gregor. This is the unpleasant episode that occurred between Gregor and his family and also the boarders, centered on the music played by Grete.