After a couple of weeks of doing high cadence riding neglecting my large chain ring (on a triple), I went to shift up and nothing happened. Must be the cable tension, I thought. When I tried to adjust it via the barrel adjuster it would not budge either way. I WD-40'd it then lubed it up, the adjuster and cable, to no avail. This is my 'good' bike with DA components (FD Chorus) so there is no dirt or rusting involved.
The limit stops are fine.
EDIT NO dirt, rusting