I feel slightly unexpected vibration when folding the device. Is my device faulty?

Samsung is aware that some Galaxy Z Flip users may experience this occurrence. 

Because the vibration motor is mounted on the top and along the edge, the force generated when opening and closing the Galaxy Z Flip is transmitted to the vibrating motor, which can cause the motor coil to vibrate slightly.

Due to this hardware characteristic, slight vibrations may be detected when folding the Device, but this does not affect the device’s performances or features.

All Samsung smartphones undergo rigorous internal inspection tests, and are always being controlled under Samsung’s high level of quality standards.