A reader electro-optically reads symbols by image capture to obtain read data, and a controller processes symbol images of the symbols captured by the reader, and decodes the read data to obtain symbol data indicative of the associated products. The controller also collects time-to-decode metadata by determining the decode time periods that are taken for the symbol data to be successfully decoded, associates the decode time periods with the symbol images, stores the longest decode time period and its associated symbol image, and displays the stored symbol image associated with the stored longest decode time period to determine a cause of the reading performance of the reader.