Permissions are fine (inherited) and checking effective permissions everything is AOK.
As you can see i can make a file in the docs folder but not the pdf_docs subfolder.
The folder has a lot of files and is quite large- i wonder if i've reached a limit? I couldn't find anything on google.
Size: 51.0 GB (54,819,804,885 bytes) Size on disk: 52.0 GB (55,925,719,040) Contains 554,697 Files
EDIT I've just checked and i can delete files... and for every file i delete i appear to be able to create a new one. This definitely points toward a limit in terms of number of files?