Or a php timeout? Perhaps increase the log level to get more information. It is strange that it is just the client, what could be different is that the client creates chunks (I can’t remember if it was 5, 10 or 20 MB) and then use a parallel upload (by default it was 4). Check out the documentation, you can as well change the chunking size (the chunks are placed in a temporary folder before being recombined). Just to point out a few things which could go wrong.