The cooldown sweep for the extra action button is too small:
https://i.imgur.com/PJuZ0Yi.png

I verified that this is still an issue with fresh Dominos settings, only changes are: for Extra Bar: Scale = 80, Show Blizzard Texture = Unchecked.

Addon Version
8.3.0-retail

World of Warcraft Version
Retail

Does it look like that without Dominos enabled?

Looks okay without Dominos enabled: https://i.imgur.com/O5iYwFC.png

Seems from the Blizzard XML that the cooldown frame has a fixed offset from the extra action button:

<Cooldown name="$parentCooldown" inherits="CooldownFrameTemplate" parentKey="cooldown">
    <Anchors>
        <Anchor point="TOPLEFT" x="5" y="-4"/>
        <Anchor point="BOTTOMRIGHT" x="-5" y="5"/>
    </Anchors> 
</Cooldown>

So my current workaround is just:

ExtraActionButton1Cooldown:ClearAllPoints()
ExtraActionButton1Cooldown:SetAllPoints()

Try the 8.3.1-beta when its gets built:
https://github.com/tullamods/Dominos/releases/tag/8.3.1-beta

Appears to be fixed. Thanks.