Maybe your computer drive has better error correction capabilities than your PS3 or standalone player. That is, maybe it overlooks any errors on the disc whereas the others are getting stuck.

Saying that, I will ask - what exactly happens when you try to play the discs on your standalone player or PS3?

Honestly - the discs being region-free should have nothing to do with it, unless by some strange quirk your standalone and PS3 won't play region-free discs