You’re not going crazy. Customers are experiencing intermittent failures when synching WSUS.
When running standalone WSUS or System Center Configuration Manager integrated with WSUS, software update synchronizations may fail on an intermittent basis, while subsequent synchronizations may be successful.
According to the newly created article, Microsoft knows the problem, knows it exists, and can even suggest a temporary workaround, which is…
Synchronization/import of previously failed definition updates should be successful with subsequent software update synchronizations.
However, the cause is still To be determined.