Stuck Shower Diverter

Attached is a pic of it.
Stuck shower diverter. That s where the valve is located. Shower diverters come in 3 different types tee two or three valve. A couple of sprays gets things loosened up and working again jackson tutt.
It doesn t take a genius to realize this. Over time the hard water in our area leaves deposits in the moving parts of the plumbing. There are several reasons why shower diverter stuck occurs.
Bathtub diverters sit in the tub s faucet where you must pull up on the post on the top of the spout to divert the water to the shower head. You may want to replace the corroded nuts or bib washer. This is because it often doubles as a shower diverter gate.
The material that causes of stuck shower diverter will finish. The holes become so smooth once again you can not believe this. This is how to fix a shower diverter.
The three valve diverter two valve diverter and tee diverter. It makes you realize that you buy a new shower head. If the shower faucet diverter is stuck because the washers are old and have broken or the plastic valve diverter inside the pipe has broken then it is time to replace the faucet itself.
Wanted to get inputs on how to fix or better replace it without replacing the whole tap and shower unit. Obviously when you are not getting enough water flowing from your shower head there could really be a problem. A simple test would be opening the bathtub faucet to check if there is a normal flow of water.