Both of these errors may be indicative of another error occurring within guest processing. In Hyper-V backups, this may occur on the host or storage snapshots themselves. In many cases, you can verify if this is an inherent system or configuration issue by executing a native Windows Backup on the guest, or in the case of Hyper-V backup configured for OnHost, a native VM backup.
For assistance with investigation of the core issue or verifying information posed in any event logging, please open a Veeam Support case.