[Tristan Lall]

Easy answer: don't mount it where it's going to get hit! (Or shield it.)

Somewhat more complicated answer: this could be a manufacturing problem related to a series of poorly-tapped mounting holes. It could also be an inadequate piece of aluminum—maybe the wrong temper or alloy, leading to unexpectedly low pullout strength. Maybe the tie rods are threaded with too small a thread in the first place—but it's hard to say for sure what's adequate, since I doubt that BaneBots intended that the gearbox be exposed to large tensile loads. (Does it look like the thread was scraped off of either the tie rods or the inside of the holes?)

Do you have any pictures of the failed parts?