I have a situation where a few keyframes on the timeline are dimmed. Using the next/previous keyframe navigation will never stop on them. When you put the playhead on the keyframe the control never shows the little dot in the circle. When I drag that keyframe left/right it will change from dimmed to not dimmed and is then selectable via navigation and so on.
So the question is, what the heck does that dimmed state mean?
I found a note in the documentation with reference to scaling a keyframe sequence. It said that operation might create "sub-frame" keyframes. Sub-frame keyframe are not editable until moved onto a frame.
That sounds a heck of a lot like what I am seeing. However, I have never scaled any keyframe sequence. I've just dragged keyframes left/right.