Workers fortifying walls and leaving traps unbuilt
Traps are not built as a priority over fortification
Game Version:
Steam Public
Platform:
Windows
Traps are not built as a priority over fortification
Another point is that workers always finish a task (if not interrupted) before looking for a new one.
When there is a moment where workers do not find any other task than to fortify walls,
they will start to fortify a wall and will finish this task (which takes some time),
even if other tasks get available after they started.
But this doesn't mean they prioritize fortifying walls.
Defense construction always has a higher priority over Fortifying UNLESS you dropped a worker on a tile to manually assign him a task, in which case it looks for the nearest task and does that task as it's main focus, even continuing that same task multiple times (fortifying more than 1 wall). Chances are you dropped the worker next to a wall (closer to the wall than it was to the defense blueprint) and he assumed you wanted it fortified rather than the defense built.
Whilst a little annoying for you in this instance, this is intended behaviour so isn't a bug.