For the OTA channels issue, it sounds like the 'Favorite channels' feature may have been causing the appearance of missing OTA channels? This feature moves channels from their standard numerical order placement in the channel guide, into a 'Favorites' section at the top, based on the channels you use most frequently. You can disable this feature in Settings>TV inputs>Antenna TV>Favorite channels.
As far as the issue you are seeing when streaming Netflix, I'd recommend trying the following:
1. Remove the Netflix channel from the Roku TV home screen by navigating to the channel tile, pressing the * key and choosing 'Remove channel'.
2. Restart your TV from Settings>System>Power>System restart
3. Once your TV starts up again, add the Netflix channel back once more, and play content again.
If you're still seeing an issue from there, please feel free to send me a PM and I'll help take a closer look to see what else we can recommend.
Something I reported while it was still in beta, and I believe is still an issue, is that when Favorites are enabled on the TV's channel listing, some OTA stations disappear from the grid completely. They don't appear within the Favorites area, nor anywhere else in the channel grid. The only way to make them appear again in the grid is to disable Favorites.