Dead space 3 freezing all the time randomly

Playing on ps3. I have found that disabling the internet connection- not just signing out of psn- will allow me to play the game with no freezes. or loss of save files. The only problem is that you cannot do any co-op missions. or complete the game!!!. I have back up copies of my save files so when i have tried going back online to try a co=op mission- like marker containment- and the game freezes on the elevator ride back out- I can reload my save. What a waste of time this game has turned out to be.  I did manage to talk to an "upper level" game tech at EA. He was the one that suggested i load the game on another of my ps3's (have 8) disconnect the internet and play a completely unupdated version of the game. Worked fine for standard game and new game plus all the way through the final battle. I then reconnected to the web, let the game update itself, redownloaded all my add ons, and continued playing levels i had missed an item. (always copying my save file) all is fine unless i try a co=op mission. freezes on the way out of the missions. BTW- i have also found that if you are playing on a new game plus and you try going online with someone one a standard game (he is host) that your save file will magically be changed back to standard - if you manage to get a chance to exit and save- Yes- I have managed a co-op mission or 2 successfully. You also have the problem of the host changing the setting from normal to impossible after you join. this will also screw your save file. I believe they do this because they are looking for someone to join a casual or normal room and then change the setting so they can get completion credit.