Fail they will, bearings you have!
I have had a similar situation happen to my kit. This is because of the loose quality control of some of the kits that are shipped over here from China. Obviously, it was assembled with a bad set of bearings and it came apart. Mine did the exact same thing.
I was riding along and then all **** broke loose. It sounded like everything inside the engine was grinding together, yet the engine still ran. Upon opening up my magneto cover, I saw a lot of metal particles. I did not have the clutch side bearing go out but the opposite side. Both sides are the same size. I completely tore the engine apart to inspect what had happened and wouldn't you know that there was no ball bearings at all inside the crankcase? That tell's you the shoddy nature of some of these kits and what you may deal with in buying them. You have to remanufacture them yourself or inspect them and install a good set of bearings from some of these extremely cheap suppliers, especially if it came from Ebay, or some vendor buying them from China who is just wholesaling them.
But, when I found the metal shavings, it was the failure of the bearing seal that I was finding, and the ball bearings were nonexistent. Half of them were missing. I am no rocket scientist or anything, but if the ball bearings did not physically disappear, then what happened to them?
Nevertheless, I ordered a new set of replacement bearings online manufactured in Japan I think, and that seemed to fix the problem.
I do have faith that the Chinese will endure.