Permission denied on CRUD operations on csv file used as a value for DB Table Variable

I'm trying to modify the csv file used as the default value for one DB Table project level variable during run time on a few keyword test by using a script. The operation succeeds the first time however, it gives a "Permission denied" error message the next time I do the same thing on another keyword test. I've tried setting all possible permissions into the folder/file but I still get the same issue. Any suggestions as to what else can i do to resolve this issue? 



P.S. I'm using file system object on script in order to manipulate the csv file and I make sure that I close the object afterwards.