I generate a simple custom dialog with 3 buttons using the following code:

var modalDialog = $('<div id="dialog"></div>');
modalDialog.appendTo($('body'))
modalDialog.kendoDialog({
    width: "450px",
    title: 'Title',
    closable: true,
    modal: true,
    content: 'What is your choice?',
    actions: [
        { text: 'Button 1' },
        { text: 'Button 2' },
        { text: 'Button 3' },
    ],
    animation: {
        open: {
            effects: "fade:in",
            duration: 250
        },
        close: {
            effects: "fade:out",
            duration: 250
        }
    },
});

For Kendo I use a custom download based on v2018.3.10.17 which works fine.

After creating a new custom package based in 2019.1.220 the dialog looks broken. (see image below)
Usually each of the buttons would automatically get an inline style of 33% so they stretch over the whole width of the dialog.
For some reason this doesn't work in the 2019 version anymore and is also broken in the 2019.1.115 build.

Since the documentation doesn't show this as a new layout, I guess it is a bug.