Sticky gear changes

[canyon80]

I have shimano ultegra gears, however having an issue with gear changes in middle of cassette where it is sticky, and need to double shift to get a gear change (usually causes gears to jump 2 as well). Gear changes towards top or bottom of cassette are fine though.

only additional thing to add is my bike did get dropped a couple months ago and mech hanger snapped - replaced this and got gears checked by mechanic who said everyone seemed fine at the time - and didn’t have any great problems with gear changes for next 3 or 4 rides. However on a 100 miler a couple weeks ago sticky gear change issue developed.
Is the derailleur perhaps broken or can anyone suggest something else?

thanks.

 

[Joffey]

Gear cable maybe?

 

[Ajax Bay]

@screenman ?

 

[screenman]

@screenman ?

If I said it I doubt they would take any notice.

 

[Ajax Bay]

Hang your bike up so that the frame is perfectly vertical (use spirit level) and the cassette is at eye level. Put the chain on the large ring and a middle sprocket. Looking at the cage (with the two jockey wheels) does it look vertical from behind (use and perfectly aligned with the sprocket?
Quite often after damage to the right side (eg broken hanger) the replacement hanger will not be properly vertical in both axes. This will result in rear mech misalignment and shifting not working accurately throughout the cassette. With 11sp (Ultegra in the OP's case) this is even more critical as the spacing between sprockets is less.
I'd also echo @Joffey 's comment, implicitly asking how many months/miles since the rear gear cable (inner and outer) was replaced.

 

[canyon80]

Thanks guys

 

[screenman]

Rear mech alignment, you will not be able to judge it by eye alone.

 

[Ajax Bay]

If I said it I doubt they would take any notice.

Cassandra