I have a light that is wired into a 3-Way circuit with one switch upstairs and one downstairs. There might be other lights on the same circuit, but I am not sure.

About a week ago, said light starts behaving erratically, it’s sometimes turning on without a switch being pressed, sometimes off. Already dismissed the presence of paranormal phenomena and decided to ask here.

I am not sure about if this info matters, but said light just turned off and I had to flip the 3-Way switch up (no change) and then down again to turn the light on again. Before this behaviour wasn’t present. I already thought of mice in my attic (definitive presence) and about the possible link that I have a outdoor security light with motion sensors since around 6 months. Light started acting erratically only a week ago though.

Any ideas of what might be wrong?