Add a new or a fixed-size VHDX for your data volume.
Synology software looks for specific hardware identifiers. You will need to edit your loader's configuration (usually user_config.json within the loader environment) to include: Unique identifier for the model. xpenology dsm 7 hyperv
Synology frequently updates DSM. If you update the OS via the control panel, the bootloader may break because it uses a modified Linux kernel. Add a new or a fixed-size VHDX for your data volume