Usually the advice is to flush & relube. This is not always the solution.
I've had them work perfectly fine in the hand, but as soon as you put cable tension on them, the ratcheting mechanism does not engage as it should. If this is the case, the shifter has worn too much. Whatever bearing/bushing/bit holds the pawl square & true to the ratchet wheel is no more.
New shifter time?
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I shouldn't have to "make myself more visible;" Drivers should just stop running people over.
Car dependency is a tax.