If you have some time, check out this brilliant breakdown by youtuber “The Workshop” regarding the crankshaft failures on the 2015+ Yamaha R1’s.
There was some chatter on the internet a few months after the first 2015 R1 models were released regarding spun bearings and crankshaft failures, but nothing came of it. The only issues Yamaha acknowledged were regarding the gearboxes and a recall was done.
Finally after a long time, a detailed analysis was done by this youtuber and he’s identified what may have most likely caused these failures. Essentially, the crankshaft is able to move side to side (from left to right side of the bike) and as it wears away into the bearing mounts, the balancer shaft weight hits the crank, breaking the shaft in the same spot on many, many bikes.
This theory is further backed up by marks on the crankshaft as the balancer shaft has made brief contact on a few occasions prior to the ultimate failure.
The smoking gun is also the fact that Yamaha has quietly added thrust washers to the crankshaft in 2016 onwards to stop/reduce the crank end play. Hate to say it but even with the washers, it’s only a matter of time…
This isn’t the first time Yamaha has done stuff like this! Check out this article about the 2005 onwards R1 models with the charging system failures!