Maybe it isn't your mechaincs

Here Is How A Pitcher’s Lack Of Functional Strength Effect Overall Mechanics

Poor balance. Weak within the pelvis, core, legs, and spine.

Back leg collapses. weak core and pelvis—remember, it takes core strength to keep you balanced on one leg and when you are on one leg that is equivalent to trying to hold up 2-1/2 times body weight!

Front knee upon landing cannot brace up and continues to move forward. No stabilization strength in legs or hips.

Short Stride. Poor flexibility in hips along with weak core.
Can’t develop rotational forces. Weak core and leg strength, poor backside drive from back leg.

Poor weight transfer. Can’t get into the “power position” at landing.

Opens up too soon. Flexibility and weak core.
Poor trunk flexion. Weak core which also creates back problems or sore back.

Can’t get good arm extension going into ball release. Tight hips and tight lats

arent these all mechanics?

Yes, the first part of each paragraph is the flawed mechanic, the second part is where one is lacking the strength/conditioning/flexibility/etc.