Visually appealing lamp with obstinacy

We can assemble 3 of these lamps outside by an electrician.
Since they do not have a dimmer switch, 2 of the lamps were connected to an external twilight switch.
Both the remaining third lamp and the other two live a life of its own.
Ca once every week is one of the lamps, although they are all connected to the same network.
At first I always disbelief changed the bulbs until stopped me rainy weather it. Lo and behold, the next day all the lights shone again, although the day before had no desire.
I have no idea why they go out and tackle why it hours later. The electrician is also a loss. It may be due to the lamps or at the contacts in the Lamp holder.
Anyway, if they work, these lamps are great, otherwise I would have already replaced.