Error in detect function with fasterRCNNObjectDetector

I have this error when I run:

[bboxes, scores] = detect(detector, img);

Subscript indices must either be real positive integers or logicals.

Error in fasterRCNNObjectDetector/getScoreAssociatedWithLabel (line 637)
            scores = allScores(ind)';

Error in fasterRCNNObjectDetector/detect (line 515)
                scores = getScoreAssociatedWithLabel(this, labels, allScores);

The detector was trained by me with 4000 samples, when I trained with only 200 samples it did not happend this error.

fasterRCNNObjectDetector with properties:

                ModelName: 'car'
                  Network: [1×1 vision.cnn.FastRCNN]
    RegionProposalNetwork: [1×1 vision.cnn.RegionProposalNetwork]
              MinBoxSizes: [13 22]
          BoxPyramidScale: 2
      NumBoxPyramidLevels: 3
               ClassNames: {2×1 cell}
            MinObjectSize: [13 13]

And the img is:

99x392x3 uint8

Knows someone how to solve it?