Issue adding custom fonts in to font picker in ribbon (SharePoint Online)

Hi guys,

We are experiencing a problem with a client, on a SharePoint Online site, which has first release enabled on their Office 365 tenancy.

Our Solution is a fully branded intranet, which uses a custom master page/css/etc. Part of the solution was to add some additional fonts to the font picker in the ribbon, for when editing in a rich content area. 

The highlighted area in the image below gives an example of what we were able to achieve.

An example of the CSS we used in one of our custom CSS files:

.ms-rteFontFace-custom1{
    -ms-name:"Custom 1";
    font-family: arial;
}

.ms-rteFontFace-custom2{
    -ms-name:"Custom 2";
    font-family: arial;
}

.ms-rteFontFace-custom3{
    -ms-name:"Custom 3";
    font-family: arial;
}

Everything was working fine until our client enabled first release a couple of weeks ago, which seems to have pushed through an update that has now stopped these custom fonts from being able to appear. Upon turning off first release, the fonts will reappear.

Has anyone else experienced this issue or does anyone know if:

• Microsoft have removed the ability to add custom fonts/font styles to the ribbon
• Is this an issue with the update and is it likely to be fixed
• Is there a new approach we're supposed to be using to get custom fonts/font styles in to the ribbon

Thanks