I'm wondering if it could be the insulation being worn through on a particular wire. I went through the various connections related to the blinkers, disconnecting and reconnecting them. It happens to be relatively warm right now so it's hard to troubleshoot.

 

Things to think about: Pin tension. We have issues on some of the newer cars where SRS lights will be set because of poor contact at a connector. Everything looks fine but when you check the tension of the connector you find out that the female connector is expanded slightly. Usually the female terminal should firmly grip the male terminal. Cold weather will exacerbate this condition. Also, as was stated, dissimilar metals cause corrosion and oxidation. I've replaced more A-pillar door harnesses than I care to think about because Volvo thought it would be OK to use two different kinds of metal in the male and female sides. You can barely see it but it makes circuits do all sorts of funny stuff.
Also, make sure that you have the correct bulbs and they fit in the sockets firmly. Don't go with cheap Chinese made crap either.
Make sure that you are getting proper voltage to the relay when activated, (with the bike running).
You could also try performing voltage drop tests on the affected circuits when the problem is evident. That would help to determine where the problem lies.
Just a few thoughts.

 

Had this problem on multiple late model Hondas
Take the blinker switch apart, clean out all the honda grease, clean everything inside thoroughly with turps, including rubbing the **** off the contactors, put it all back together.
They will work fine after that.