BigStitcher black square

Has anyone had a problem like this? It seem to appear during image fusion step. BigStitcher creates a black square in the middle of the image. I also stitched these tiles myself and the result didn’t show such an artifact.

This is the result from BigStitcher

This what I expect in terms of illumination

Could this be due to some sort of normalization?
The input data is uint16 and I also save it as uint16.

This is the fusion settings that I use

    // fuse dataset, save as TIFF
    run("Fuse dataset ...",
        "select=/output/best_focus/Cyc002_Reg001_CH001/dataset.xml" +
        " process_angle=[All angles]" +
        " process_channel=[All channels]" +
        " process_illumination=[All illuminations]" +
        " process_tile=[All tiles]" +
        " process_timepoint=[All Timepoints]" +
        " bounding_box=[All Views]" +
        " downsampling=1" +
        " pixel_type=[16-bit unsigned integer]" +
        " interpolation=[Linear Interpolation]" +
        " image=[Precompute Image]" +
        " interest_points_for_non_rigid=[-= Disable Non-Rigid =-]" +
        " blend produce=[Each timepoint & channel]" +
        " fused_image=[Save as (compressed) TIFF stacks]" +
        " output_file_directory=/output/processed_images/Cyc002_Reg001_CH001");