My friend and I had an old playstation 2 and it would play every game under the sun fine apart from PES1 and then PES2. We would have to caress the friggin machine to get it to even load the games! This I am sure was due to our girlfriends 'accidentally' knocking the station over repeatedly as they walked past.
The best technique we found was tilting the station ever so slightly, say five to ten degrees off standing straight up. As someone else mentioned this is not a good idea but we were desperate. Eventually when I bought a new station we were able to smash the old machine and god was that satisfying after all those hours trying to get it to work.
It did fly quite gracefully from the third storey of our house down to the road though...