For what it's worth, not an isolated instance. (Probably good; general problems tend to be easier to diagnose and fix.)
https://api.chess.com/pub/player/chidori_boruto/games/archives
{"archives":["https://api.chess.com/pub/player/chidori_boruto/games/2017/07","https://api.chess.com/pub/player/chidori_boruto/games/2017/08","https://api.chess.com/pub/player/chidori_boruto/games/2017/09","https://api.chess.com/pub/player/chidori_boruto/games/2017/10","https://api.chess.com/pub/player/chidori_boruto/games/2017/11","https://api.chess.com/pub/player/chidori_boruto/games/2017/12","https://api.chess.com/pub/player/chidori_boruto/games/2018/01"]}
https://api.chess.com/pub/player/chidori_boruto/games/2017/11
{"message":"Entity of type 'Chess\\WebBundle\\Entity\\LiveTournament' for IDs tournamentId(905759) was not found","code":0}
Since I'm looking for an archive and not a tournament, that's probably a Clue. Same error in my previous post, so the problem whatever it is looks consistent. (Again, probably good! I hate the times one symptom has two or more issues behind it!)
Came across this today:
https://api.chess.com/pub/player/baldemorski/games/archives