My Tiagra 10-speed shifters have recently been jumping multiple gears. Shifting down (from smallest cog to biggest) is fine (10-9-8-7-6-5-4-3-2-1), though maybe a little stiff. But shifting up will jump in the middle (1-2-3-4567-8-9-10) with single pushes of the paddle casing the gears to crash up multiple gears in the middle.
I've ridden 20K miles (32K Km) on this bike. The shifter cable was replaced in May, about 250 miles ago (this is my winter bike), and the rear mech was new in February.
So I'm thinking maybe the shifters are just worn out?
Or should I just replace them?
Are the shifters serviceable?
Or could it be something else? I don't think it's cable tension as I'm shifting up fine - but I'm not a mechanic so...)
Thanks for any good advice.