If you use map transformations in your items, you will get the mapped value initially (when switching from another dashboard or refreshing) then subsequent “live” updates will be without the transformation applied.
There is a discussion going on here about this inconsistency: [REST Api] Inconsistent response of REST-Api for items with mapped values · Issue #2788 · eclipse-archived/smarthome · GitHub.
There are other threads with examples on how to use a Javascript object and ng-init to translate raw values locally in the HABPanel template: Template Example: Weather Binding - #69 by Signal11