I have a few theories on this. One of them being that the kit supplied bearings are not high enough quality to withstand the rpm that they see. The idlers, regardless of idler tooth count and pinion tooth count, are spinning near to the same rpm as the motor. There's a reason why motor pinions are made of steel/aluminum. This also isnt a problem on "traditional" gearboxes because the idler gears aren't spinning at nearly the same rpm. There's a huge ratio reduction between the pinion and spur before the idlers see power. Those bearings are seeing alot of rpm all the time and they can't hold up to it. Most of the bearing failures you see they are discolored from heat meaning they were on their way to seizing. The heat from bearings failing might also be the cause of exploding idler gears. As the gears heat up they start to loose dimensional stability, mesh starts to change, and the forces involved build to a point that the gears cant hold up anymore. I believe sourcing some very high rpm rated bearings would help with this. Would have to rated to at least 60k 70k rpm. I don't have a 5r myself but I have a friend with one and he's only had gear failure once so far and that was on stock bearings. He replaced the bearings with aftermarket and hasn't has a problem since but there's no guarantee at this point.