Metal Gear Solid 3 not working on my old PS2?

This is really strange - I have three copies of Metal Gear Solid 3: Snake Eater and my old PS2, which I have had since 2002, cannot read the disc for any of the three copies of MGS3. The reason I bought the two others, was that I could not get my first copy to run on my old PS2. Every other game, besides strangely enought Metal Gear Solid 2, works on my old PS2. Now I tried running on a newer model I have of the PS2 and all the three copies of MGS3 could run, without any problems. Is these disc different than others, or what is the explanation?

When did you buy these copies?

Your old PS2 is not model number 3500. Those havehaddisc reading issues with certain games in the past. This was ressolved in the 5001 revision.