I think I know what is happening & a workaround, so mainly wanted to document this.

If you make a change to the base map, I would expect that scenarios that are locked to that aspect of the base map would reflect that change.  In fact if you go into the designer and look at those maps under both the base and derived scenario you will see this change.  But it doesn't seem to affect games until you go into the scenario and 'save'.  You don't have to make any changes to the scenario, just 'save' it and then it gets propagated to live games.

Yes that could be a bug actually - it's due to the browser caching the board data. I'll review this for a fix.