I get that evry now and again, I clean all the contacts and sometimes on the bulbs with the two elements in them only one has gone, a general cleanup and bulb swap usualy does the trick for me, I seem to get through a lot of bulbs about 4 or 5 times a year I have to have a look and change at least one
So we are talking about the pictogram display then?
I'd still say failed bulb, have you checked the roof/back window mounted bulb? Reason I ask is that I had exactly the same type of display in my Volvo, filament warning light would only come on when braking. I checked the brake lights and *both* worked.
In other words, I wasn't thinking to check the third bulb.