did anyone see issues (upload failure) while trying to upload e.g. 600 documents at once (PNGs, JPGs, PSDs, etc.). Document total size is around 600 MB.
That's a LOT of documents, I'm not surprised it failed. When something like this happens, I just break it down to maybe 50 at a time (which is still a lot.)
True, breaking it down might help, but then at the same time - the user should upload batch by batch, which means they cannot leave their PC until the upload session is completed.
