I was placing items by hand with a blueprint (using the mod "There Is My Ghost" to prevent placing the incorrect item inside a blueprint ghost), and somehow I placed several "hidden lamps" and now cannot build over them or remove them.
If I disable the Street Lamps mod, it will delete the hidden lamps along with all the other Street Lamp items.
I've placed the street lamps like this a ton and this is the first time it's done this.
This is my first time posting on the mods website, not sure if I can post pictures, but here is a link to a screen shot: https://bit.ly/2VOGQ62
I'm playing in 0.16.51

Thanks for your report. I'll take a look at this when I get some time. As mentioned in the mod description, I can't guarantee that this mod will work with every other one. I'll add this "There Is My Ghost" one to the known incompatibilities for now. It does appear that the street lamps seem to have various issues when used with blueprints, so I'll definitely be looking at it as soon as I can.

I got this bug too, I used the deconstruction tool and my construction bots came over and removed them. This causes the hidden lamps to not be removed with the powerpole and now there's a bunch of hidden lamps flashing no power warnings and the location is unusable. I've found a way to 'fix' this is to run this command:
/c for _, entity in ipairs(game.player.surface.find_entities_filtered{name="small-hidden-lamp"}) do entity.destroy() end
This will remove these hidden entities from your map, which unfortunately will mean all of them, including the ones under powerpoles you wish to keep.