I sold Mugen after I had 6 arms break in 6 heats/finals at an event interstate. Not all of them were crashes, some awkward landings, a couple literally brushing the pipe. Exact same breaks every time (through the shock cutout) I mean so exact I could have bet my house on the position of the breaks.
I put it down to heat (near 40c/104f)
bad batch of arms
bad driving (sponsoreds were breaking them too)
mugen in general/sold.
when i got home boiled some arms and returned to cooler temps/no breaks/CBF'd/sold
so I guess the best suggestion I got is to boil arms or run other brand arms