Weird Indicator issue

[PK_Irl]

Hi all

crossposting from Outback forum for more visibility as it's not a specific Outback issue

I have a 2015 Outback Diesel. Bought second hand last year but a couple of weeks back was the first time I had to use a trailer. Up to this point all lights on the car worked fine and all with normal filament bulbs, not LED replacements.

When I connected the trailer lights they all worked apart from the r/h indicator on the trailer so obviously when using that side it flashed double speed as you'd expect. However when I disconnected the trailer now the car indicators on both sides are flashing at double speed yet no bulbs are blown on the car. I even bought a new trailer light board to test with and when I connected that to the car the same issue as when using the trailer returned (ie, all lights work fine including l/h indicator at normal speed but no r/h indicator on the trailer board and both r/h and l/h indicators flashing at double speed when light board disconnected. To put the cherry on top, the hazard lights flash at the normal speed.

Any ideas what might be wrong? I checked the owners manual and can't find where the fuse for the indicators are just in case that might be a problem. Is there a seperate fuse for the trailer light socket? I am presuming the wiring was done in the dealer but no evidence obviously. It;s a 13-pin socket with a 7-pin adapter. Removing the adapter makes no difference. I disconnected the Battery to see if that might reset the ECU but no joy. Torque Pro app isn't throwing any error codes (well apart from one about low voltage on a glow plug which happened a week after the indicator issue).

I'm stumped but maybe one of you guys might know?