When an FCV op observer observes an insert or an update to the admin.system.version collection, it registers a commit handler to set the FCV version. However this logic can throw an exception if it gets interrupted, for instance if a stepdown occurs. In particular, the call to killSessionsAbortUnpreparedTransactions ends up calling OperationContext::waitForConditionOrInterrupt. This is an issue because commit/rollback handlers are not allowed to throw exceptions.