a peculiar error with sftp

Whenever I sftped a particular gzipped file to a particular directory and then try to unzip it, I get Permission Denied error.

With this file even I cannot do chmod. though the file permissions are -rw-r--r--

When same file I sftp to a different location I am able to gunzip it.

Directory itself cannot be a problem, because I sftped many other files to same directory with same set of file permissions and was able to gunzip it easily...

Though with a round about of transferring file to another directory my work is done...but I am still wondering what else can be reason.

Any thoughts on this?