OK, I finally figured out what the bug is in the new control panel that keeps throwing up an error when you try to change whois.
You have to uncheck this box (see above) and make sure all contact types are exactly the same. So if you are adding a business name you will have to add it to Registrant Contact, Admin Contact, and Technical Contact. Please note note every domain will show a technical contact and the tabs could vary from domain to domain but the important part is to make sure they are all the same and whois will update in the new control panel.
I have not tried this on bulk edit but it will probably fail because the tabs are not the same for all domains.
Gonna tag
@FM because with this new info his team may be able to diagnose this issue further.
I am happy to announce this is the last bug I have found in the control panel, everything else is fixed and running smooth as far as I can tell.