Originally Posted by
MetinUz
I doubt this has anything to do with the chainline, at least not when there is a problem when at the outer chainring. Is the rear shift cable slack when you shift to the smallest cog?
+1 ...The chainline affects how the chain feeds onto the lower pulley, but won't affect how the chain feeds out of the top pulley onto the cogs.
IthaDan also made good points as to possibly why the derailer won't retract fully to the last cog position.
Possibly also there is a problem with the cable sliding freely in the rear cable housing. The derailer must snap smartly to the last-cog position in response to the shifter's command, but won't if the return spring isn't providing enough tension or if the cabling action isn't smooth.