I got a FS100 off Ebay from a place where I have purchased before and I noticed the last FS100 I got has a Pulsing like tick sound sound (Seems like once per second) that only happens when recording. It does not pick up in the recording when I have an wireless mic pack attached and selected (So it does not get picked up internally). It does however get picked up in the recording when I have the external mic because it picks up the ambient sounds. Has anyone ever had this problem and may know what it is?