Live TV fails with playback error on original

Playback of Live TV on the LG Plex app throws an error if “Original” quality (default) is selected.

Switching to a transcoded resolution is fine.

Switching then back to Original also works.

Error: “playback error - an unexpected playback problem occurred”

Same backend (both wired) on Shield works fine.

Server Version#: 1.42.2.10156
Player Version#: Plex for LG 5.93.2 Platform: 10.2.1
Tuner: HDHomeRun Quattro (DVB-T)

I suspect that it is because the video is 1080i. Plex does not natively support 1080i playback. Plex will transcode 1080i to 1080p.

Perhaps then the issue is it’s not transcoding automatically interlaced to progressive on the WebOS app. Shield works fine with the same sources so I can’t put it down to anything else.