Gopher to the Sleuth Gods
I'm in Delhi, working " The Unique Riddle of the Haunting Phantom" when I get a message that I cannot visit the Postal Clerk at all. Then I notice that one of the alibis is the Curator. No curator in Delhi.
Yeah, I think the case files still being full is definitely the most likely explanation. The suspect alibis are set when a mystery is created, and they're stored as strings, eg. "Curator". There's nothing in the game that changes those alibis once they've been made, so with the case saying it was started in London, with all the alibis being London townies and your having had your apartment in London previously; I'm leaning towards thinking your study wasn't empty.
All that said there really should be a check on Sleuth's end that all studies are empty before an apartment is moved.