Button on sitemap don't work

Setup, Configuration and Use Items & Sitemaps
1

Hi all,

I’ve got my Things, Items and a sitemap set up on openHAB 3. Good start!
But when I click on the switch in the sitemap, nothing happens. I get an message in openhab.log though:

Confirmation received for unsend command. Sequence number: 0

Things:

Bridge milight:bridgeV6:F0FE6B62C62A [ host="192.168.1.20", bridgeid="F0FE6B62C62A", passwordByte1=0, passwordByte2=0, repeat=2, delayTime=75 ] {
    Thing rgbwwLed all "All Lights" @ "Everywhere" [ zone="0" ]
    Thing rgbwwLed living_room "Living Room Light" @ "Living room" [ zone="1" ]
    Thing rgbwwLed bedroom "Bedroom Lights" @ "Bedroom" [ zone="2" ]
    Thing rgbwwLed office "Office Light" @ "Office" [ zone="3" ]
    Thing rgbwwLed bathroom "Bathroom Lights" @ "Bathroom" [ zone="4" ]
}

Items:

Switch office "Office" {channel="milight:rgbwwLed:F0FE6B62C62A:office:ledbrightness"}
Switch office_nightmode "Night Mode: Office" {channel="milight:rgbwwLed:F0FE6B62C62A:office:lednightmode"}
Switch office_whitemode "White Mode: Office" {channel="milight:rgbwwLed:F0FE6B62C62A:office:ledwhitemode", autoupdate="false"}
Dimmer office_brightness "Brightness: Office" {channel="milight:rgbwwLed:F0FE6B62C62A:office:ledbrightness"}
Color office_color "Color: Office" {channel="milight:rgbwwLed:F0FE6B62C62A:office:ledcolor"}
Dimmer office_speed "Animation Speed: Office" {channel="milight:rgbwwLed:F0FE6B62C62A:office:animation_speed_relative"}
Number office_mode "Animation Mode: Office" {channel="milight:rgbwwLed:F0FE6B62C62A:office:animation_mode"}
Dimmer office_mode_relative "Animation Mode Relative: Office" {channel="milight:rgbwwLed:F0FE6B62C62A:office:animation_mode_relative"}

Note: it includes :office:, instead of :3: for example. With :3: it it says the link is not correct, but with :office: it seems to work.

Sitemap:

    Frame label="Lights" {
        Switch icon="lightbulb" item=office_whitemode label="Office Lights" mappings=[ON='White Mode']
    }
}

Anybody have an idea what I do wrong here?
I know the command types nightMode and whiteMode are stateless and should be configured as pushbuttons as they only support a trigger action. I believe I set it up that way, as it is according to the instructions at: https://www.openhab.org/addons/bindings/milight/