ProcedureKit: malloc: *** error for object ...: incorrect checksum for freed object - object was probably modified after being freed

Since 2.7.1 I am observing occasional crashes with the above error message. The crash happens in Operation class in state property setter, either on willChangeValueForKey("State") or didChangeValueForKey("State"). I observed it on both simulator and iPhone running iOS 9.2. Any ideas about the cause and fix for this? Thank you.