When you release a key on a real harpsichord, the plectrum returns to its original position, and a damper stops the string from vibrating. However, as the plectrum returns, it sometimes lightly brushes against the string again, creating a very subtle, brief sound. This is a characteristic of how a real harpsichord operates and is part of its authentic sound.
This brief sound upon key release is not a defect or malfunction of your Roland piano. Instead, it’s an intentional feature that adds to the realism of the harpsichord sound, giving you a more authentic playing experience.