If you use the pipette tool to move one of the poles around, which have now lights attached to them, they are moved but remain as an entity where they were, so you won't be able to place anything where they were.

This is the mod - https://mods.factorio.com/mod/PickerExtended

I will look into it thanks for the bug report

This same thing, where the 'light' is sort of a separate entity, is also causing Blueprinting/copy issues, e.g. when you already have the poles up, but are trying to blueprint red and blue circuit connections to them, it says "Unknown key: 'entity-name.pole-lamp' is in the way" so it won't connect the circuit wires from the copy/paste/blueprint