Dropbox file delta meta contains two path infos - one used for api/oauth signature and another is physical filename.  The former is always lower case while the latter is actual case-sensitive name.   To save deploy payload size, we simplified by sending just one (physical) path info which we literally use to create the file on repository.  When talking to the API, however, we lower the case to match the signature.   I concluded these by observing other Dropbox client implementation which is working.