I've been talking this through in my head for about an hour now and yes they do have a common circuit. Turn signal goes on and sends power up to the gauge cluster to activate the turn signal indicator, could a bad GROUND be our common denominator? If the ground for the gauge cluster is not very good it might work a bit till it gets loaded up with several things being on and stop working?
Like I said I've been talking in my head so this might still be in my head and I'm not really typing this???