Interesting. I have a similar problem on my face lifted 156 (Jan 2003 registration).
Since November, both my indicators and hazards have been working intermittently. Some mornings they don't work (or do eventually by the time I get to work), sometimes they don't in the evenings as well. They flash fine when unlocking and locking the car.
Assumed it was related to the cold weather, but it has got warmer recently, and this week they haven't worked at all. It's always both the indicators and the hazards so could this be the relay?
What connections in the engine did you spray Shambeko? Hadn't thought of that.
If it is the relay, is it easy to inspect / replace? Presumably it is near the fusebox under the drivers side, and just needs to be pulled out?