CX-5 Muffer and Exhaust Leak Warranty?

Along with cleaning the muffler and pipe flange and buying a new gasket, what sealant would be appropriate to help with the small leaks from irregularities of the connection?

Permatex Copper Spray-A-Gasket Hi Temp Adhesive Sealant or something similar?
 
Shouldn't the gasket fill any voids?

If it didn't I think I might try a different gasket, or maybe add another somehow.
 
It should, however mine still leaks slightly from the top of the flange. Both sides have been sanded and cleaned but the issue remains. Maybe, somehow, the flange or pipes became misaligned/askew.

I'm buying a new gasket to replace the previous one purchased last year and would like to add something that will help void the minor gap.
 
It is best to just use a gasket, I think the Permatex exhaust sealer cures into a tough glue that will be hard to get off next time.
 
Once I tried using some kind of exhaust repair material but it couldn't fill a very large void. It seemed to resist heat ok.

Maybe some pics of the problem would help find a good solution.
 
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