What are the bugs in distributed systems?

As a seasoned practitioner in the realm of cryptocurrency and finance, I am intrigued by the complexities inherent in distributed systems. Could you elaborate on the nature of bugs that commonly plague such systems? Are they unique to the decentralized architecture, or do they share similarities with bugs encountered in traditional centralized systems? Additionally, how do these bugs impact the security, scalability, and overall reliability of distributed ledgers like blockchain, and what strategies are employed to mitigate their occurrence and effects?