Logic X Vocals Dropping Out

Hi... I hope someone is able to help me....

A recent event occurred which has never happened in my Logic X before... I noticed that when playing back a track the vocals would fade out for about 5 seconds and then fade back in again... After trying many different things i realised it was my Antares Auto Tune Plug in (AU)..... If i disable this, the problem doesn't happen. However i would very much like to use this plug in... Does anyone know why the plug in is causing this. I can use the Logic Default tuning system for now but it is not as professional sounding as the Antares one. I have also checked in the 'Options tab' and increased the buffer seconds to the maximum allowed limit so i don't think that is the issue. In terms of my mac its self its a:

2.7 GHz Intel Core i7

16 GB 1600 MHz DDR3

NVIDIA GeForce GT 650M 1024 MB

Hope someone can help!!

Thanks,

Morris