synthesizers are not recording all the notes

hey all!

I just bought an M-Audio Keystation 61. It connects via USB. Loving it so far.

I had no problem connecting it to Garageband. It's working fantastic.

The issue I am having:

if I play an arpeggiator in GB, or any synthesizer, they sound fine when I am just messing around. But the moment I record, only 20% of what I am playing comes through!!

so instead of playing a full arpeggiated chord, GB record the top note.

it's super weird and of course very frustrating.

Any ideas would be HUGELY appreciated.