reversing light and indicator light fault indication

Hi, I'm new to this forum so please bear with me if this is an old chestnut. Yesterday, I disconnected my trailer after which the indicators worked at twice their normal speed (just as if a bulb had blown) each time I start the car I get a fault indication saying reversing lights and indicators are faulty. Actually the reversing lights are fine, it's just the indicators that are fast -I checked all indicators and they are all working. Strangely, the hazards work at their proper speed. I've tried disconnecting the battery waiting 5 minutes and then reconnecting it, but the problem persists.
Has anyone any ideas on what has happened and if this is a fault I can clear or is it a garage job maybe needing new parts?
Many thanks in advance for reading this.
Nige.

Welcome to the forum C3Nige

Is this a standard fit citroen electrics for the trailer or an after market job?

It sound to me like there is a problem with the trailer relay or its wiring.

https://uk-trailer-parts.co.uk
The diagram shows the aftermarket trailer relay and the wires that get used.

Hi C3 Driver52,
Thanks for taking the trouble to reply. The trailer wiring is supplied & fitted by my local Citroen agent (Bollingmores). In the past, whenever I connected the trailer I would get an error message saying rev. lights faulty which I assumed was because there are no rev. lights on the trailer. As soon as the trailer was disconnected everything worked normally. Actually, since I posted the problem it has now gone and the car is working normally! Maybe there is a problem with the connections in the towbar socket - I will check them out when the weather improves.
Regards, Nige.