Hello @m1entus,
After deeper dive into the issue it looks like Apple did some changes in internal CoreBluetooth implementation. Crash appears consistently when multiple instances of CBCentralManager are using different dispatch queues working in parallel. We’ve reported this issue as a bug to Apple and waiting for their fix. In the meantime we’ve released Estimote iOS SDK in version 4.25.3 that fixes ESTBeaconDevice class. We are also working on another, much wider, temporary solution that will prevent this crash in other parts of the Estimote SDK. I will keep you updated.