Of course, no one will record on video everything that happens on the screen every time he spends time in an online casino in order to have all the evidence on hand, or you are not a star who is obliged to do it according to the contract, but it can also play in the opposite direction, in the case of OP, we really have just a story from the first person.
This story will remain only listened to from one side as Stake isn't really going to come up here and explain a very simple thing to OP which has already been explained by a lot of users within this thread. It wasn't the casino's fault if he couldn't redeem his bet and the scores were equalized, it is a normal thing that when a match is being live-streamed, there is a delay of about 7 to 10 seconds for it to reach the audience, and so there is a delay in the casinos that offer live betting as well.
So if someone like OP tries to redeem or cancel the bet in between that delay interval, they would definitely not be able to, and that is exactly what happened. The scores changed in between the delay provided by the casino and the live stream, so OP couldn't redeem since his team wasn't winning anymore based on the score.