Yes, you can delete unwanted angles if you wish. Do it in PgcEdit (double click on the movie PGC and click Del Angles down the bottom - see the help file) and clean up in VobBlanker after only 1 angle remains (angles take heaps of space). Be sure to pick the correct angle to keep! You can view the various angle cells by clicking the |> at the right of each cell. Sometimes, they correspond to things in different languages. Usually, angle 1 is the one to keep but check out the others, too.
Or, also in PgcEdit, you can try to manoeuvre the VTSs around so the VTS with the angles isn't right at the layer break. From the menu: DVD --> Remap titlesets. Again, read the help file for details.
Regards