Failover Cluster crashing during backup after 2025 update

[dasfliege]

We've in-place upgraded our 6-node Hyper-V 2022 cluster to 2025. Everything was working fine until we raised the cluster function level to 2025.
Since then, when we start the veeam backups (on-host), some of the nodes immediately are at 99% CPU, stop responding and disconnect (timeout) several CSVs.
We are already troubleshooting the issue with MS, but i wondered if there are any other people facing the same problems, since it seems to be directly related to backup operations or other heavy load operations on the hosts.
Veeam Case 07912704

[david.domask]

Hi Florin,

Thank you for sharing the case number and sorry to hear about the difficulties.

I can see Support has already begun the investigation and requested additional information you provided, so please continue with Support as they will be able to better comment after a review of the debug logs. At first blush, not aware of issues related specifically to increasing the functional cluster level, so please continue with Support on the investigation.