A migration from an image mode VDisk will use the source managed disk group and the source managed disk group assumes the combined state of the image mode MDisk and the managed disk group. If the online or offline states of the image mode MDisk and the managed disk group are different on different nodes, the source VDisk might go offline or all of the VDisks in the source managed disk group might go offline.
For each node, note the online or offline states of the source VDisk and the source managed disk group. If one entity is online and the other is offline, bring online whichever is offline. Taking the online entity offline is not recommended because other VDisks might go offline.