Hello, since this never had a clear resolution, here is explanation of the bug and why it happens:
There is a bug in disk iteration in that XO vmware plugin (somewhere in that esxi.mjs I don't remember exact location) - it basically expects that all disks of VM exist in same datastore and if they don't it crashes as the next disk in unexpectedly missing (undefined)
Workaround is rather simple - select the VM in vmware, migrate -> storage, disable DRS (important) and then select any DS that no disks current exist on. If you select and DS that is already used by same VM it will sometimes not get fixed! It also may happen even if VM is "apparently" looking like it's on single DS, even if it reports as such, still try to migrate it to another DS, and disable DRS so that really all files, even meta files are in same directory.
Then run XO import again, it will magically work.