Duplicating local folder in absolute path from LESS file which is imported (@import) to other LESS file in T3 BS3 Blank Template

[inscriptios]

I'm using /localhost/templates/t3_bs3_blank/local folder to keep changes when T3 BS3 Blank Template is updated. In that folder I have template.less file and a few of LESS files which are imported into template.less. For example start of template.less file contents:

@import "vertical_menu.less";

If I'm using the following code in the imported files:

.sm-parent dl.level1 > .parent::after {
  background-image: url('../images/icons/vertical-menu-angle-icon.png') !important;
}

absolute path to the PNG image is http://localhost/templates/t3_bs3_blank/local/local/images/icons/vertical-menu-angle-icon.png - the local folder is duplicated in the path.

If I'm using the same code in the template.less file then the absolute path to the PNG image is http://localhost/templates/t3_bs3_blank/local/images/icons/vertical-menu-angle-icon.png - the local folder is NOT duplicated there.