Character changing its orientation randomly while calling the animation through scripting

Hi

My team is facing a typical problem.After exporting the animations into unity3D(pro)through Maya (as fbx) the characters are randomly changing their orientation axis instead of walking/running through the given path through scripting.

Ex: We have made the character run through a specific path,in the middle all of a sudden his orientation changes and starts running in the air.These things are happening at random intervals when ever we are checking the animations through scripting.

In another case we are calling particular animation say death2 which is a substitute of death1 through scripting but the engine could detect only death1 and is not granting to play death2 through scripting,it still plays death1 animation.Why it is so?

We are in the critical path of our project please help us to fix this problem.

Thank you

Siddhartha