Originally Posted by dddd

The detent springs in Campagnolo Ergolevers usually need replacing at every 15k miles or so of typical riding. These are inexpensive.
First they yield and weaken, then they break. There are two in each lever. There are springs for left levers and mirror-image ones for right levers.

The left-side shifter's springs last about 3x that time as right side springs do.

There are youtube videos showing full Ergolever rebuild.