I had the same issue in the Fallout 4 thread, where I was trying out the feature for the first time. I was using the pasting from clipboard method and during each attempt the failure seemed to happen after the second or third image. They were large images prior to the automatic cropping and I worked around it by manually cropping the ones that failed and trying again. Wonder if there’s some sort of buffer limit involved.
Edit: something similar may have struck Telefrog in the Wonder Woman movie thread today.