@Depechie Your current bootloader image is attached as sata0, right? So detach it, download new version of arc loader, attach as sata0 (qm set ....), run VM, prepare new bootloader (select model, version etc) - all those steps are the same as a fresh install. After that open web browser, connect to you NAS IP. Wizard will detect DSM installed on drives and allow you to "migrate" without losing you data.