Anti-skating problem

I have an unusual problem, it does not matter how much I adjust the anti-skating on my turntable (Oracle delphi V - SME309 and Grado Sonata) I can never get the left channel to sound as detail as the right. I must admit that they are pretty close, (same output levels, same amount of details and depth) but if a play a choral work, (like a Bach's cantatas) I hear the "Shh" from the chorus on the right channel, but very little from the left. Can anyone tell me what's wrong? I checked VTA, Tracking force, Azimuth and the level of the turntable and all are correct.

Any help would be appreciated.

Miguel