in this particular Champions match (I've seen this issue at others) the match timer color is different than the in-game overlay, so there's just a rectangle that looks really out of place. Image here:
https://imgur.com/a/gv6mW1O
I see this at some events, but not at some others.. cmon Riot, it's been 2 fucking years. This shouldn't be happening at the most coveted event of the year. This is a really basic issue, please solve it