Turn signal only works with high beam on - 2006 S60 Volvo

My roommate has a 2006 S60 Volvo. One day the passenger turn signal just stopped working. It only works if the high beam is on. The driver side turn signal works fine and so do the emergency flashers. It’s not the bulb, not the fuse, not the turn signal lever, and she even took it in the shop and they couldn’t figure out the problem without replacing the DIM which would cost a lot.

Anyone have any ideas?

I wonder if there is a bad ground for the front light unit on the right hand side. When the headlights are on high beam, enough current flows to overcome the resistance in the bad ground. My only reason for making this guess is that years ago, we had a problem in our house and half the house lost power. All the fuses were good. However, we could restore power by turning on the clothes dryer. It turned out that there was a loose connection in the electric meter for one leg of the line coming into the house. Turning on the 240 volt clothes dryer drew enough current to overcome the resistance in the loose connection at the meter.
Unfortunately, this doesn’t explain why the emergency flashers work on both sides. My second guess is that the bulb in the front is wrong–possibly a single filament bulb where a double filament is required. You might try putting in new bulbs on the right side, making sure that the bulbs are the type called for in the owner’s manual.