Ps2 problem with Metal Gear 3

Could anyone please help me wth a question.My son has a ps2 and I just got him the game Metal gear 3,but it won’t play on his.It does play on a freinds ps2 Machine.I have noticed that my son’s ps2 will only seem to play the Blood Red disc’s,it won’t play any of the silver coded disc’s. And sense MG3 is for PS2 which he has I can’t understand why.I could not afford a new PS2 so I managed to get him a decent used one or so I thought.I had read about all this copying and switching with PS2’s and I wonder could have somene switched laser’s so it will only read the Blood Red disc’s.All info is welcome and would be greatly appreciated by my son and I,Ty very much

Some PS2 models have a very bad dvd player. The laser doesn’t get enough power to read all the discs perfectly. Another cause can be an old modchip, because they derive power from the same connection that the laser unit uses.

If you’re good with electronics you can replace the laser unit yourself, but it’s not that easy.

Well thanks so much anyway I do appreciate your time and response to my Question and my son says hi!.I guess we’ll just take it back and save up for a new one.Thanks again.

Yea I had to replace TWO ps2s cause of bad lasers. You could try ajusting the POT levels (no not weed)
http://member.telpacific.com.au/kwetiaw/Ps2_Repair_Guide.pdf