It could be that the recording has two violin players on it but it could be a setup issue with phasing or speaker placement, the speakers too far apart from one another.
Violin Moves All Over the Sound Stage
I have a beautiful digital recording of Isaac Stern and the NY Philharmonic playing the Beethoven Violin Concerto in D Major. The solo violin sounds sometimes in the center, sometimes from the left speaker and sometimes like two different violins in two different locations. What is wrong?