"RENDER NOT FOUND" when audio source has been mixed down

Hi

We encounter "RENDER NOT FOUND" error, when we execute Web API call, "checkSequenceIsReadyForXfer" to a scequence which has audio source pre-processed "audio mix down".

We don't get such error if the same audio source has not been processed "audio mix down".

This happens regardless the source format is XDCAM or DNxHD.

The WebService version is, v.3.0.9.

The detail of the error message is, "RENDER_NOT_FOUND:There were unrendered effects:There are unrendered effects in this sequence."

Could you please advise if this is a software bug, or the operational error ?

Thanks