Autosampler Distortion Help

I'm a new MainStage user but a long-time digital recording engineer. I upgraded to MainStage 3 recently, mainly because I wanted to use the auto sampler feature to sample a favorite upright electric keyboard of mine. After installing MainStage and setting up midi and audio interfaces I was able to get an external instrument channel set up from the keyboard and it sounded good. The problem is, when I load up the auto sampler plugin on that channel and try to test-play notes, they come through with some serious phase-type distortion. I'm not talking a little flanging here, it's more like saw wave synth distorted keyboard instead of the beautiful grand piano sound that I've come to love. Any ideas on a fix?

Here are my specs:

OS 10.9.5

Core i7

ram 32 gig

solid state hard drives

tascam us-122L (yeah, I know but it sounds fine on all my other ins and outs for MainStage)

Axiom 61 midi controller

synth to be sampled: technics sx-pr700