Adding an "STL Check" modifier after the 'Editable Poly' will fix the problem. You can then collapse it as well, this will turn the Editable Poly into a Editable Mesh but you can convert it to Editable Poly again with a Edit Poly modifier. Modifier madness, hehe :P
@musashidan You might also want to try seeing if the Edge Selection option in chamfer modifier is useful for you - the modifier also selects an additional edge in the inner corner for a smoother chamfer, but the chamfer modifier in a general case generates uglier topology connecting to it.
Your error happens because you're having dragCommand on Pine, which is the same slider you're modifying. You want to have dragCommand on oak do you not? :) Currently: pineSlider -> dragCommand -> Modify Pine You want: oakSlider -> dragCommand -> Modify Pine
If you're object has modifiers and you're working on the base level, the snap doesn't work right. A specific example would be working on an editable poly object with a turbosmooth modifier. Snap will only work correctly if you temporarily turn off the turbosmooth modifier.