EasyEDA v. 5.6.15 The Rebuild All Copper Area function either needs to execute automatically before exporting Gerber files (preferred)  or at least needs to put up a warning if the copper areas have changed before exporting Gerbers.  It's very easy to make a small change (like adding vias to a 4-layer board), save the board and export the Gerbers and forget to rebuild the copper areas.  This happened to me and I ended up with a batch of ruined boards with shorted power planes.  Since the copper areas are rebuilt when the file is re-opened its very hard to see what happened.  In my case I had the original bad Gerbers but could only see the problem by using another company's 3-D Gerber viewer to find the bad vias in the inner layers. The copper areas should be rebuilt automatically when the user tries to export the Gerbers.  Ideally the affected copper areas should rebuild in real time when vias and pads are added or changed, but at least EasyEDA should verify they're rebuilt before exporting Gerbers.