I posted a video on youtube showing exactly what the problem is - is this your problem too?
http://www.youtube.com/watch?v=08FbFn-qsT8
maybe you could refer the engineering department to this video
I will call monday to try to send this replacement back - for me the macbook is unusable like this since 1) I travel a lot and it makes listening to audio while travelling impossible, and 2) my work involves playing audio out through this port
to be fair the socket on the replacement is a little better than the first which was very very loose - but the problem is still there and I can imagine it will only get worse with wear
besides a change in design the only solution for me would be an apple non-standard headphone jack to universal headphone jack adaptor
this seems crazy - I'm surprised not more people are experiencing this - beginning to think I'm paranoid
now I'm hoping that apple will sell me a previous revision macbook pro to replace my old powerbook