Subitles for Operas recorded from MEZZO channel

Hi, I'm hoping you can help with a recording issue on Optik/TV+.

We watch the MEZZO channel, which broadcasts operas, and some of these have English subtitles. When we set a recording, the subtitles are (sometimes? always?) missing from the recorded version, even when we've turned on Closed Captioning in the box's settings beforehand.

A few questions:

1. Is MEZZO's subtitle track being transmitted as closed captioning (a selectable track) or as "open" subtitles burned into the picture? If it's a selectable track, does the box actually record that stream, or only decode it for live viewing?
2. I've seen a number of posts on the TELUS community forum describing closed captions working on live TV but failing (partially or fully) on recorded playback through the set-top box, while working correctly when the same recording is viewed through the TV+ app or telustvplus.com. Is this a known issue, and is there a fix or workaround for viewing on the box itself? We want to watch on our TV, with our home theatre system.
3. Is there a setting we're missing that would let us reliably capture subtitles when recording from MEZZO specifically? We have a “smart” LG TV that presumably has any setting we would need.

We'd really appreciate any help getting this working . Thank you.