This is strange. I am not quite sure why this is happening, but it looks like the player does not like when the display is set to none. I had to call jwplayer().setup() again on the <div> to get the video working again:
We are running into this issue as well. I have confirmed in both JW 7.2.4 and 7.3.0-beta in Chrome / Firefox stable. It does not seem to be reproducible on Android / iOS or Safari with _native_ HLS support.
Possibly a Flash related bug?
See OP's associated GitHub Issue here: https://github.com/jwplayer/jwplayer/issues/1047