Cannot escape raw HTML with {{{payload}}} into ui-template - page hangs

I'm looking to output some raw HTML within a dashboard template, but when I add the extra {} pair - i.e. change from {{msg!.payload}} to {{{msg!.payload}}} - the page hangs - a 'loading...' screen sits there for a minute or two and then produces a blank page. I'm on Node Red v3.1.5 and @flowfuse/node-red-dashboard v1.1.0.