Hi @addisonklinke. In my case i made a mistake with the index corresponding to batch size. Whenever i used a batch size > 1 (rarely because of gpu restrictions), i could not copy the whole tensor into the new one, which resulted in the error. But my traceback pointed to conv3d layer(as shown in my post) instead of the copy operation 2 lines before, which made it confusing.
For your second question: I havn’t used pytorch > 0.4 or coco dataset, so i am not sure about it. One thing i know is that the default collate function (pytorch 0.4) use torch.stack function call, which expects the input tensors to have same shape (i had input tensors of different shape). So if coco has images of same shape, then there is no need to use custom collate function. I am neither familiar with captions in your case nor with the latest pytorch releases, sorry.