We need to wait for the day when 3D_clip code is invented to totally solve this problem.
But for now, you need to choose a better CKPT and you would get much better hands.
There are only few ckpts are high quality which you need to notice.
Mix Ckpts are mostly crash in generating hands.
There's only a few ways
Control Net - By far the most reliable way. Either find a picture that has good hands already and use that, or if you want to get fancy, use depth mapths of the hands in the right position + the depth library extension to overlay the depth map hands on the right spot on your image, then use control net depth mode to make the hands better
The various hands embeddings + Envy Better Hands lycoris -They are not perfect, but they help sometimes usually kind of
RNG - Just mass generate a bajillion images trying to brute force it
RNG + Inpainting - Inpaint the janky hands then generate a bajillion images at varying strength trying to get one that looks normal
Overall your best bet by far is control net