I tested what you said, it sounded like this might be the thing but...
I just live migrated a VM that that uses physical RDM between two hosts. The device is set as "mapped raw lun", and the compatibility mode is physical. So something doesn't add up here. I'll try to see about the vRDM if it makes changes things.
I wouldn't struggle if I were you. The struggling, unfortunately, is my burden in this case. It's a pretty complex scenario, and I'm not sure I'm allowed to get into details anyway.
(Your help is appreciated though 
)
Any other thoughts?