When loading stock via imports (such as from M3) the SKU description is automatically set to be the same as the style. This is by design because every SKU (dimensioned item) should be a different size/colour/material of the same style. 

If for some reason there is a difference in the SKU labels versus style whenever the style is loaded the SKU labels will update. The only way to correct this is to SQL update the SKUs affected. This is a temporary work-around and the permanent fix is to create new styles for the items in question.