If you scan thick film, such as black & white film, and your images are a bit overexposed, it is possible that the final scan is too bright, overexposed and almost white if you scan with Multi-Exposure (ME). Activate the Multi-Exposure preview, to see the image with Multi-Exposure as a preview and to avoid deviations between preview and final image.
Multi-Exposure (ME) increases the dynamic range of the scanner and tries to make more detail visible in the dark areas. An overexposed negative is brighter, because of the light. However, with negatives, you have to think in reverse. The images themselves are very dark and thick. So there is a lot of information in the dark areas, so in those areas Multi-Exposure has a lot of influence. There is probably information on the film that the scanner cannot capture without Multi-Exposure. Without ME preview, you edit the image without having all the data which leads to differences during the final scan with ME. The preview with ME takes advantage of this data already for the preview so that there are no differences afterwards.