Custom slider appears in wrong location

Tried to add a couple of sliders using custom control and the docs. Want to control light and fan. Both sliders appears top left in the web page, instead of the expected location together with other controls. Have tried MS Edge, Chrome and Safari browsers with same result.

Anyone have any clue on this one?

OctoPrint 1.5.3
Python 3.7.3
OctoPi 0.18.0

controls:
-   children:
    -   children:
        -   command: M1010 S4 P%(speed)s
            input:
            -   default: 100
                name: Fan Speed
                parameter: speed
                slider:
                    max: '100'
                    min: '0'
                    step: '5'
            name: Fan ON
        -   command: M1010 S4 P0
            name: Fan OFF
        layout: horizontal
    -   children:
        -   command: M1010 S3 P%(power)s
            input:
            -   default: 100
                name: Brightness
                parameter: power
                slider:
                    max: '100'
                    min: '0'
                    step: '10'
            name: LED ON
        -   command: M1010 S3 P0
            name: LED OFF
        layout: horizontal
    layout: vertical
    name: SnapMaker Enclosure