So.... this just cost me this grand arena

There is supposed to be a tiny < symbol where that barely visible orange hand is pointing. In your case there is only an even less visible rectangle. That's what you're supposed to click to make this nuisance go away. Took me a moment too. What a fun mini game that was! I mean, it's not like these 15% datacrons make a timeout extremely likely as it is.

I still managed to finish my first fight and then the game crashed in the next one. Closed the turn order tracker after a restart, no more crashes. So that thing stays permanently closed now and this GAC round is likely a loss.