Smush Pro cannot find images

I can't optimezed all of the images by Smush Pro. I'm getting the following errors:
http://i.prntscr.com/vjN38W64Q5ipY-rdIbWFNQ.png

I've checked and those images are presend on the server, but they have a slight difference in their names. As an example, Smush Pro is looking for bileciki-do-prezentów-do-wydrukowania-5-150x150.jpg, but on the server, the image is called bileciki-do-prezentow-do-wydrukowania-5-150x150.jpg.
Can this be the cause of the issue?