Texture Errors

Don't know about the displacement lines, but you should be able to bring back the Undo/Redo buttons under the View menu, and there's probably Undo/Redo command that you'll have to tick

in the texture application window, you have to edit the texture shift, so that the texture transitions smoothly.

Or better select one face and rightclick with holded alt-key (or was it ctrl?) on the other face.

DasMatze

Might be a lighting issue then. Sometimes freaky stuff happens.

That screenshot is in hammer---the line probably wont be there once you run vrad and are in game.

click 'camera' in the top left of the 3D view, there are many modes to pick from, personally I swap between wireframe, Textured shaded polygons and 3D textured. If you are in textured shaded polygons overlays will flicker something terrible but all the brushes are shaded depending on what angle each face is pointing, making large areas of the same texture FAR easier to navigate in 3D. When I care about overlays or texture alignment with displacements I swap to the other textured one, I can never remember the name, I just know its the other textured one to 'textured shaded polygons' This stops overlays flickering and removes any shading so its dead easy to see when tetxtures align. Then every now and then working with displacements I'll swap to wireframe.

Why do you need the buttons?, Just hit Ctrl+Z(Undo) And Ctrl+Y(Redo)