1.
RGB output problem on Sony DVP-NS900
You've got a bit of reading to do!!
In short though, there is a problem that the voltages coming out of the scart socket are not to specification, resulting in the switching between AV channels. Sony were modifying this by shorting the two relevant pins I think but this removes the functionality altogether. If memory serves me correct, other batches appeared without the problem once Sony got their act together. I have a Toshiba 28Z05B so I don't know if I have the problem with my NS900 but if I did I probably wouldn't be bothered with it!
Contact your local Sony dealer/repair centre etc etc.
2. This is normal. The laser "thing-a-me-jig" has to move from one layer of the disc to the other for dual layered discs. Some players are better than others in dealing with this. Saying this some DVD manufacturers are better than others as to where the layer change gets placed in the middle of the film!