In user forums (e.g. for the Lexon Flip Premium version), several people report a slight rattling or clicking noise when the alarm clock is turned or tipped over. A slight internal noise can therefore be normal and no cause for concern; it usually indicates loose but non-critical components within the mechanism. As other users have reported similar observations and the function otherwise remains flawless, it is probably a harmless design feature.
However, if the noise still bothers you or you want to be absolutely sure, we recommend replacing the device before you give it away.