when converting onnx to tmfile, the flatten layer converted wrong

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As following pictures. One is the onnx model and the other is tmfile.

The last flatten layer got wrongly converted, which resulted the output layer with wrong dims. The correct output layer should be 1x128, but we got 1x512x1x128.

I tried onnx with opset=9, 11, and 13, but all derived the same wrong flatten layer conversion.

Any suggestion?

Thanks in advance.