I'm sorry that my first post is one asking for help. I have looked but can't find a similar post. I have an issue with my rear derailleur on a Felt F75 with Shimano 105.

The problem is I can shift from largest down to smallest and back up again in sequence ok. However if I go into the middle of the cassette (11-28) when shifting up and down one cog at a time (starting in the opposite direction to the original shifts) nothing happens the derailleur hardly moves.

This does work however when you get into the top large cogs which makes me wonder if it is a tension thing?

The bike got soaked at weekend so I decided to clean the cable as shifting was that smooth on the ride. I didn't remove the cable just unclamped it to get rid of tension and squirted it with Muc-Off Bike Spray.

I would appreciate it if anyone has any pointers. Thanks!