Acrobat pro does not release the file handle when the file is closed in reading pane

To recap and explain:

I have a program which is generating the pdf file each time reusing the same file, and if the file has been opened in Acrobat it  cannot recrate the file - of course. But even closing the file in acrobat's reading pane does not release access to update the file.

BUT after some experimenting I see that it is not systematic - some times it works as expected and some times I need to close Acrobat. So it is very unclear what this issue is.

It cannot be exclude that it can be related to the fact that the file is located on a file server both when it works and not works as expected. I will post if I get more details on this.