AndyRJ
Player Valuation: £2.5m
That volume of water isn't just getting in from somewhere due to poor design. There's a clear issue with the roof, potentially the rainwater outlet. Given it's in the corner, then this is likely where the rainwater outlet/downpipe is so there's likely an issue with that.
Worry about it if it happens during a match day after opening and not when the stadium isn't finished yet. Granted, you wouldn't expect it to be happening at this stage but It's an obvious issue that LoR will be aware of and need to sort.