The 1987, Great performances recording? For me the violin stays center left... but it seems the frequency determines the exact location. Sometimes far left and sometimes center left. Does this sound similar to what you observed?
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?