Failed to read X Samples Error

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Hi - I'm getting this error message;

Writing AAF file
Adding assets to AAF file
Adding essence for asset [Auto-detected stereo] to AAF file
Adding essence data to AAF file for portion 0 of asset [Auto-detected stereo]
Reading audio data from audio extractor : 262144 samples
Failed to read 262144 samples

No AAF file has been generated.
X2Pro Audio Convert LE 3.0.2


I'm using;
FCPX 10.2.2
OS X 10.10.5

"Trim embedded audio" is not selected
"Trim handles" is not selected

Thanks for your help,
Rich