We have been seeing this issue for many years and Shimano North America has finally issued a voluntary recall for affected cranksets. We are an authorized service shop that can inspect, start a claim, and send your crankset in for replacement if yours is affected. No charge to you from Shimano or us during this entire process. Please stop by the shop for a quick inspection if you think yours is affected.
Here are the details:
Hazard: Bonded crank parts can separate and break, posing a crash hazard to consumers
Product: Pre-July 2019 11-speed bonded hollowtech road cranksets
Remedy: Inspect (authorized service shop) and replace if necessary. If replacement needed due to product showing signs of bonding separation or delamination, a free replacement crankset and installation will be provided by Shimano.
Cranksets Possibly Affected and More Info: https://www.cpsc.gov/Recalls/2023/Shimano-Recalls-Cranksets-for-Bicycles-Due-to-Crash-Hazard
Check the link above for the specific cranksets in the voluntary recall and see if yours is one of them. If so, then come by the shop and let us give it an inspection and send it off for you if affected.
Be safe out there and keep the rubber side down!