cracked rotor on velineon

[vashon10]

I realize this is an older thread, but I recently cracked a (new replacement) rotor in my Velineon after only 2 packs (3s, 5000mah). I'm rather puzzled how this could happen running it within spec (temps, rpms). It was in a stampede geared 21/86 with mashers.

I noticed the balance epoxy had come off one end of the rotor and smeared inside the can. Could that have jammed and caused the crack ?