Issues with compilation of YAML to CSS

Hi,
I have this issue with compilation of CSS, no idea where to start to debug this issue.
This is the problem/error:

The code around this section looks like this:

tablet-popup-border-style: 1.5px solid rgba(0,0,0,0.2)
  tablet-popup-align-dialog: center
  tablet-popup-margin-top: 0px

  ####################################################
  #                                                  #
  #                     CARD-MOD                     #
  #                                                  #
  ####################################################

  card-mod-theme: tablet

  card-mod-root: |
    #view {
      background: url('/local/background.png');
      background-size: cover;
    }

  card-mod-view-yaml: |
    .: |
      hui-view {
        background: none !important;
      }

    #################################################
    #                                               #
    #              GRID CARD HEADINGS               #
    #                                               #
    #################################################

    grid-layout$:
      hui-grid-card:
        .: |
          hui-grid-card {
            padding-bottom: 1vw;
          }

And yes, I’m using a copy of matt8707 dashboard config