I will check the Add resource from URL today and report back.
As far as the HTML component ( or any component for that matter ), when a timeline restarts the component will blink since it must replay.
Imagine if you have a Video, if the timeline restarts, the video must restart playing from the beginning as this is the logical behavior.
However, we are working on a feature now that if you have only a SINGLE resource on one channel, and that channel restarts, you will not see the blink. This feature is needed for our Kiosk and that is why we are adding it.
Hope this help,
David.