FTP - Unable to write to a directory named 'lib'

Hi,

Is there any security policy in PLESK that may result in restricting FTP write access to any directory named like 'lib' or 'etc', ?

Issue :

I have created a 'mj' FTP user via PLESK, to access a spécific directory : "/dev.trunk-v2" which points in fact to "/var/www/vhosts/c014.eskis.eskis.wk-factory.com/dev.trunk-v2"

In this directory, among a bunch of others on which I have no write access isssues, there is a 'lib' directory, with the following rights :

drwxr-xr-x 25 wkf_clt_014...

FTP - Unable to write to a directory named 'lib'