ORIGINAL: nonstoprc
That the mount for the muffler tail end allows some play could be of help.
Adding a support for the end of the header (e.g., with a stainless steel strip mounted onto engine's cylinder head screws) definitely will fix it for all.
The broken header probably can be brazed back with the yellow brazing rod sold by DA + a propane torch.
good advice on supporting the ends of the headers.that will strengthen and isolate them from the flex and vibration of your engine vs. the airframe. Adding a brace between the two will also help.As well as making sure you have some space in the flex coupling between the headers and cans to allow for vibration and flex.
Flex pipes tend to leak between the coils (depending whose it is) and crack easily