Strange issue with grid in replicator

This is my code:

fields:
  content:
    type: hidden

  button_grid:
    display: Button
    type: grid
    starting_rows: 1
    min_rows: 1
    max_rows: 1
    fields:
      text:
        display: Text
        type: text
        width: 50%
      url:
        display: URL
        type: text
        width: 50%

  my_replicator_field:
      type: replicator
      instructions: |
        Replicate a new set for each piece of content you need.

      sets:

        content_set:
          display: Testset 1
          type: grid
          starting_rows: 1
          min_rows: 1
          max_rows: 1
          fields:
            text:
              display: Text
              type: text
              width: 50%
            url:
              display: URL
              type: text
              width: 50%

        content2_set:
          display: Testset 2
          type: grid
          starting_rows: 1
          min_rows: 1
          max_rows: 1
          fields:
            text:
              display: Text
              type: text
              width: 50%
            url:
              display: URL
              type: text
              width: 50%

This is what it looks like: