We have recently noticed that the API call server.GetPlayerCombinedInfoRequest is no longer including the DisplayName in the response. We have been using this call in a cloudscript handler to let players check out a different player's profile, and it was working as expected until recently (one or two days ago, we aren't sure).
We set the GetPlayerProfile flag in the request as true, and we do get the PlayerProfile in the response, but it does not include the DisplayName. It does include PublisherId, TitleId, PlayerId and LastLogin.
For now, we have implemented a workaround adding another API call, server.GetPlayerProfile, which does include the DisplayName in the response, but this is obviously inefficient.
As I mentioned, it was all working fine until recently, and now it's failing consistently (and we haven't touched our code). I haven't seen any note about this in the release notes, so I'm flagging this in case there's a bug somewhere!