Our two DAG members (mailbox/cas) servers are members of our parent domain, xyz.com. When users in xyz.com login to OWA, everything works as advertised. When a user from a child domain, sub.xyz.com logs into OWA, they can not access certain items under Options.
For instance, "Automatic Replies", they see an error presented from OWA which says "The operation couldn't be performed because object 'sub.xyz.com/MarketingDeptOU/Smith, John' couldn't be found on 'domaincontroller1.sub.xyz.com'.
If the user clicks on other options like Mark As Read, Message options, Block or allow, Conversations, Email signature, or Read Receipts (and some others), they see a different error. "There was a problem loading your options. Please try again".
This seems to be affecting all users in our child domain. and i think (highly) that this was the behavior since we rolled out Exchange 2016 (an upgrade from 2013). Although it took a week for our first trouble ticket to come in.
As a workaround, users can click on OTHER. Then "Go to the earlier version". Then, in the 2013-style Options menu, they are able to access everything OK.