Auto-sandboxing app issue

I am not a security geek, but found an issue when using Auto-sandbox rule for specific application.
For better security when reading pdf files, I added rule for pdf reader to open virtually always. It works, but only sometimes.
For example when download a new pdf and open - it runs virtually as it should.
Second time I open the very same pdf it is no longer running virtually.
Thx in advance for responds.

Any advices how to set rule so app runs sandboxed everytime ?

Now comodo decided to don´t sandbox always. I set rules for all possible situations and it´s not working.
And if someone thinks I use Adobre reader with autosandboxing feature - no I don´t. My program to open pdf files is Sumatra PDF.

Can you show or explain exactly the auto-sandbox rule you have for PDFs? Did you make the rule for your PDF viewr application or just .pdf file extension?