TLDR; I can't figure out where the value for %appdata% is set for RDS servers. This appears to be different from the "Remote Desktop Services User Profile" directory in ADUC, as I can successfully manipulate that value and have it propagate.
I am attempting to moving RDS user profiles from one server to another. I've robocopy'd all of the profiles over to the new share and have shared it, and confirmed it is functional with my regular user account. Even though the fields in ADUC are populated with the new server information, the change does not trickle down.
I've come across a Powershell script that will search all of the GPOs, and when I searched for the old server name I found a policy that was also redirecting AppData (Roaming) in
User Configuration / Policies / Windows Settings / Folder Redirection / AppData (Roaming)
And I changed that to the new server, ran gpupdate /force on my RDS server, and logged in. When I run gpresult /r I see it shows the correct share for the Roaming Profile field. When I echo %appdata% it still shows the old share. I cleared this GPO and updated with no noticeable change.
When I clear the contents of the RDS user profile field in ADUC, gpresult /r still shows me as having the correct Roaming Profile value, but makes me a local profile (which is reflected in echo'ing %appdata%). In gpresult /r the Roaming Profile field is now blank.
When I set the contents of the RDS user profile field in ADUC to the new share, %appdata% shows the old share (likely from the GPO mentioned above) and gpresult /r shows the new share. What is curious is that %appdata% shows \oldserver\tsprofiles$\Application Data rather than AppData like I would expect.
It should be mentioned that this is a fairly old domain (est. 2008), and started out with both Domain and Forest functional levels at 2003. They are currently 2008 R2 (this project is getting rid of the last two 2008 R2 servers in the domain). During this testing I've authenticated to each of the 3 domain controllers currently running (2 are 2008 R2), and have checked DCDIAG and replication status and found no issues.
So at this point I think I have established that the RDS User Profile directory is not being set through ADUC, but the population of that ADUC field matters. It isn't being set through GPO that I can find, so it would stand to reason it is being cached somewhere or something.