Relative phase

[Gary]

I am using the audioInjector in a phase sensitive application with quadrature left and right line in. The problem is, the relative phase of the two input channels seems to vary slightly with time. I am also using the headphone output at the same time. Is it possible that due to running input and output at the same time that some input samples are delayed or advanced in time? If I did not use output, would the phase be steady or is this a characteristic of I2S?