1.Material Quality is King:
TLDR: Crafting quality got nerfed when using lower rarity material. So it's best to achieve your desired rarity through materials.
For example when crafting petalshard:
2. Give a 5% Margin of Error:
While the calculator has been accurate thusfar, there may be some variables that we dont know yet
3. Use as Much Crafting Quality as Possible:
If you're doing a high rarity craft you should always be trying to achieve the highest crafting quality.