OK some more testing....
I'm using Mii Box 3 android boxes, which have been updated to Android TV 8.0 (oreo).
Using Perfect Player 1.4.6, with decoder set to "Auto", all 3 C-SPAN channels and CCTV work without issues.
Using OK2 apk however, it is not as simple
With Decoder set to Native: CCTV works fine... However I cannot even stream any of the C-SPAN channels.. I get the spinning spindle when I select the channel, and then it just goes red and stops.. Tried that with all 3 C-SPAN channels and always the same issue. It's as if it doesn't recognize the stream or something.
With Decoder set to Software: CCTV I only get Audio, But all the C-SPAN channels work fine.
With Decoder set to Hardware: CCTV I only get Audio, but all the C-SPAN channels work fine.
I've pretty much switched to Perfect player as my daily player. Takes a little longer to start I find. But overall it is more stable I find. Still has some issues occasionally, but nothing I can't live with until I decide to just get a buzz box