This problem persists in PMS 1.32.5.7349. Looks like it was noticed at least 22 months ago:
Previews work fine after part 1 in the Plex Web Player and on Roku (tested with a Premiere and Ultra). This is with both the supported “partX” naming convention as well as the undocumented “(Part X)” naming. I’m fairly certain this is a bug. Whether it’s a player bug on Android TV clients or with PMS, I’m not sure.
