Including image styles in custom module
Your problem is don't delete image style when uninstall module. So when you reinstall image style already exist. Use can use hook_uninstall to delete 
image style to finish uninstall: write code in file module_name.install

&lt;?php
use Drupal\image\Entity\ImageStyle;

function module_name_uninstall() {

  ImageStyle::load('image_style_name')-&gt;delete();

}