Fabrics can acquire shiny patches if they are ironed at high temperatures especially if the garment surface ironed is uneven, such as pocket or fold line below the garment.
The shine or imprint is not permanent and will come off if you wash the garment.
Avoid ironing over seams or folds or you can place a cotton cloth over the area to be ironed to avoid imprints. Ironing the article inside out will also help avoid shiny patches. You can also try a lower temperature setting.
The spray function should not be used on delicate fabrics because it could cause stains.