The most common reason an STL file may be not quite right is a mechanical connection where some piece isn’t quite as the designer expected, so the 3D model that interfaces with it no longer fits.

Cura supports the most common file formats, like OBJ, STL, DAE, 3MF, and DAE. You can do basic file editing in Cura before slicing. For example, you can rotate and scale the file along the XYZ axis.