Screenshot here:
This happens when scrolling out to 60-70% on Firefox to get a normal sized view.
Same for me (Waterfox latest version which is based on Firefox 60 ESR) even in 100% mode.
Also this screenshot demonstrates another issue: the current time control of watched games is not visible any longer. You can see the remaining time of both players but not the exact format (1+0 or 1+2 or 10+10). So, for example, you don't see the increment which is very important in order to understand the dynamic of the game.
Update:
This works for me know. Thanks to the Lichess team for fixing it quickly!
TV broken for me (although Waterfox 56.2.9 (64-bit) isn't listed in Supported Browsers; OS font scaling is 125% on 1080p)