Just saw this the other night.
I have backlight "in app" set to gesture, after dark.
Originally it didn't always recognize it. That appeared to be fixed, except it's only half-fixed. It appears the watch is ALSO honoring "Do not disturb" hours when in-app.
No, no, no no and no! It should honor them when in WATCH mode (obviously) but not when in an app. When in an app "DND" hours should be IGNORED!
Otherwise, as soon as DND hours start if you're in an app (e.g. running, at night) your gesture for the backlight becomes inoperative! This also means that if you have other notifies set you won't get them even if in an app.
If I'm in an app DND hours should be ignored. If you started an app you're not sleeping, obviously, and you're doing something where you're alert, awake, and, well, "active".
That's a bug, IMHO. I reported it although I didn't realize it's probably linked to the DND hours when I emailed the report last evening.
Please look into this one Garmin!