CC button not appearing sometimes when course loads
I noticed an inconsistent issue. This is a single slide course with a video with CC, published in HTML5 mode only. It uses the modern style player.
Most of the times the CC button appears, but sometimes, mainly in Firefox it doesn't. I think it has to do with the network speed and initialization of the player, like it is not able to detect in time that the video has captions and it doesn't initialize the CC button in the player (not in the DOM).
I solved it adding a dummy layer with a button that shows the layer with the video. This seems to give it time for all to initialize correctly. But just in case you can review the initialization of the CC button logic to be more robust.