Speculation here, but I'm staying with the idea of a reaction of Guardsman polish to your Hekman topcoat for it to cause the fogging issue. I've seen that happen before on pieces and Guardsman is pretty well known for 'ducking' any liability issues for their product. That's who you should be contacting I think, but it will be tilting at windmills since they rarely respond favorably to any customer complaint and repair request.
The horse is already out of the barn on this one I'm afraid, but in the future follow the manufacturers recommendations for products to be used on their pieces or use at your own risk. Anything that is non-silicone based is generally OK (that a very general 'generally'!). Its always a good idea to test a new polish on the backside of a piece and let it be for a few months. Most compatibility issues don't happen immediately but take time to break down the topcoat.
One longshot idea. Did anything hot land on that spot? A pizzabox, a casserole dish? Anything like that?
Duane Collie
Straight answers from thirty-six years in the business.
My Private Messages are Disabled - Please ask questions here in the forum.