My round 18" Ellipsoids, well one of them, became not so round on the back inside edge.
Not sure where/when it happened, and it's balanced up fine, but you could see the edge move in/out slightly when the wheel was on the balancing machine. A bit soft bend (not a localised dink)
I can imagine with really hard/firm tyres and even smaller sidewalls, that a good hard dink can crack the alloy rather than bend it as in my case.
Two routes, they are either bendy, or crack. I'd go with the bendy option... you can always get it repaired relatively easily. But cracks, hmmmm...
That said, anyone remember when the biturbo RS4 came out? Those 18" multispokes bent like they were made of cheese. Almost every owner had new wheels eventually (must have changed the alloy!?)
No real fix for this, it's just the price you pay too have 19" wheels and RFT I'd imagine. Throw on a normal tyre and I bet the cracks are more likely to end up as bends/dinks that can be straightened out.
Dave