easily fixable. You'll need things:
-drill
-drill bit the same size or slightly larger than the threads of the screw
-wooden dowel the same size as your drill bit OR precut wooden plugs of the desired size
-wood glue
-sharp knife/fine saw
remove the speaker. Drill out each hole. Cut the dowel into plugs that are slightly longer than the box walls are thick. Cover the plugs in a light layer of wood glue and push them into the drilled out holes make sure you use enough glue to seal the hole. Wait 15 minutes. Use sharp knife/fine saw to trim the plug flush with the box. Rotate speaker slightly, mark new holes, and reinstall mounting screws.