My 1 year old X5 equipped bike is starting to not shift properly. Need ideas from you guys regarding how to fix it.

Going from the second to the third small gear in the back, the shifting hesitate a bit before shifting. And actually to make it shift I have to over shift the trigger shifter so that it jumps to that gear). The problem only occurs in that gear. Doesn't matter if I am on small, middle, or big chainring. All other gears shift fine and there is no over derailling.

I tried giving more tension in the shifter barrel, and tried giving less, with same result, or better shifting on all up gear and down shifting doesn't work well, or vice versa.

On top of that, the gear indicator stop working correctly. When I am on the biggest cog in the back, the shift indicator is only showing I am on the middle cogs.

All of this start occuring last Friday afternoon, after leaving the bike in the car for the entire day while I am at work. But in all my years of riding that has never really been a problem.

Tried taking out the cable and oiling it already. My biggest woe is that it is still not shifting correctly from the second to the third smallest gear in the back. Can care less about the indicator not working.

I know X5 is a pretty cheap part, but I did like to try fixing it some more before replacing it.

Any idea on how to fix this?