2012 3008 & 2018 208
I had exactly the same thing, intermittent to start and eventually constant which is when I found the wire had actually snapped... so it looks like a bit of common fault!I have had this intermittent fault on my 2015 Peugeot 308 for some months. The local garage said the error was with the drivers seat side airbag and said it needed to be looked at by a Peugeot dealer. I decided to have a look myself so took the seat out of the car - easy and removed the plastic cover from the side - not so easy.
There is a wiring loom containing 3 wires that runs up the right hand side of the seat to the airbag. I noticed that this had been trapped in the seat metalwork that allows the seat back to incline. The wiring loom outer cover was broken and the insulation on one of the wires crushed exposing the conductor which I assume was intermittently making contact with the seat metal work and causing the fault. Repaired with several layers of insulating tape and route of loom moved to avoid the "pinch point".
The problem has not come back for three days now so hopefully that was the cause. The routing of the wiring loom is not good so maybe this is the cause of problems being had by others.