Why does Chrome on Android replace my .vjs-text-track-display captions with its dumb native captions (sometimes)?

[tanuu]

I'm still using Videojs 4.6.4 because - so I'm told - one of the “happy accidents” of Video.js 4.x is that it leaves the <track> element in the DOM and lets you style captions with CSS like any other element. So you can set font-size, color and line-height in videojs.css and use those styles in your .VTT caption files instead of video::cue. On my site I've also set .vjs-text-track-display to display as a table-cell; height: 100%; width: 100%; which allows positioning captions anywhere on the video. So things like this are possible in the VTT file:

03:11.000 --> 03:12.000
<p class="center-middle big fade-out">Text text text

These VTT-with-CSS files render as intended in most browsers and OSs I've tested - e.g. Chrome & Firefox on Windows, Safari on iphones/ipad, Firefox on android. So, it's a great feature for combining your video with some flashy captions styled however you please.

But lately I've discovered that - sometimes - Chrome and Samsung Internet on Android ignore .vjs-text-track-display p and render them as boring native captions centered at the bottom of the screen. It doesn't happen always - in fact most times it displays the styled <track> captions as intended, but maybe 1 out of 5 times it doesn't. How can a bug be so random? What's going on "under the hood/bonnet"? Any ideas?