It doesn't take much of the wet stuff to create enough damage that the best solution is a rebuild.
That cracked or split sump filter may only be a symptom...
If you have two friction plates that are identical, except for the inside diameter of the friction material, then you need to identify the mean effective radius of each plate.
When installing steel plates of different thickness in a clutch drum, the placement of the thinner plates can be important. And, the ideal placement of those plates depends on which clutch drum you’re using.