Wanted to point out what looks like a bug with this endpoint. Steps to repro:
1. in a Spotify app, obtain an access token with the implicit grant flow (1h expiration I believe)
2. Use it to create a player with the web playback SDK. Verify that you can use PUT https://api.spotify.com/v1/me/player/play to play tracks on this player, as expected.
3. Wait more than an hour. Try to use this endpoint again. You will receive a 401 response with the message " this access token has expired", yet the player will actually start to play what was requested.