python-plexapi: playMedia() on Nvidia Shield causes subscription failures

When sending a Client().playMedia() command, it seems that this command (which only specifies the server’s port) will cause the Plex app on Nvidia Shield devices to treat the plexapi request source as an actively listening controller. The Shield client will send POST requests back to the plexapi host on the server’s port which repeatedly fail.

Example logs from Shield:

02-26 21:58:39.517  i: [pms] /10.6.9.55:57992 - GET /player/timeline/subscribe
02-26 21:58:39.517  i: [Now Playing] New subscriber 0xcfe9033bf0a4 at 10.6.9.55:32400 with command id 23
02-26 21:58:39.519  i: Fetching [method:POST] http://10.6.9.55:32400/:/timeline?X-Plex-Token=...HBKU&includeExternalMedia=1
02-26 21:58:39.525  i: Time out fetching http://10.6.9.55:32400/:/timeline?X-Plex-Token=...HBKU.
02-26 21:58:39.667  i: [pms] /10.6.9.55:57996 - GET /player/playback/playMedia
02-26 21:58:43.325  i: Fetching [method:POST] http://10.6.9.55:32400/:/timeline?X-Plex-Token=...HBKU&includeExternalMedia=1
02-26 21:58:43.333  i: Time out fetching http://10.6.9.55:32400/:/timeline?X-Plex-Token=...HBKU.
02-26 21:58:44.383  i: Fetching [method:POST] http://10.6.9.55:32400/:/timeline?X-Plex-Token=...HBKU&includeExternalMedia=1
02-26 21:58:44.395  i: Time out fetching http://10.6.9.55:32400/:/timeline?X-Plex-Token=...HBKU.
02-26 21:58:45.382  i: Fetching [method:POST] http://10.6.9.55:32400/:/timeline?X-Plex-Token=...HBKU&includeExternalMedia=1
02-26 21:58:45.386  i: Time out fetching http://10.6.9.55:32400/:/timeline?X-Plex-Token=...HBKU.
02-26 21:58:46.384  i: Fetching [method:POST] http://10.6.9.55:32400/:/timeline?X-Plex-Token=...HBKU&includeExternalMedia=1