I've got a Shimano Nexus 8 IGH, and was previously able to adjust it properly by aligning the two yellow tick marks in the 'window' as described here.
However, I then removed and replaced the rear wheel a couple of times to change a tire, clean, etc. However, I can now no longer see the second (outside) yellow tick mark in the window, and can't seem to get the gear adjustment dialed in without it. I have been using the painted yellow tick marks, but lining them up doesn't seem to dial in the shifting quite as nicely as it did when I lined up the tick marks in the window. Any idea what went wrong, and how I can get the second tick mark back again?
EDIT: It looks like someone added a photo--thanks. My issue is that when I look at my hub, the second (bottom in this photo) tick mark is not visible no matter what I do, so I can't use it for alignment. The window is clean, and the first tick mark is clearly visible.