DJM-S5 Blinking FX Button

Hello,

I recently purchased a demo model DJM-S5 from Sweetwater.com.  It is hooked up to 2 turntables and my Mac running Serato.  When I power the mixer on, everything seems normal.  Once I plug the USB into the computer, the FX buttons illuminate and the FX1 button blinks continuously.  If I press the FX2, FX3, and so on, the blinking switches to the newly pressed button.

I am new to the modern style of mixer with Serato etc so maybe it is inexperience.  If someone could help me figure out if this is normal or there is a problem I would appreciate it.  I can provide a video if necessary. 

Thanks,

Jake