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Arbitrage opportunities appear all the time but close just as fast as there is always someone looking for them, I really think that we are getting to the point in which sport gamblers that want to take advantages of such windows need to create their own bots similarly to what it is happening already with trading, besides casinos do not like this so they could limit your account or close it as they do not like gamblers that always take the best possible lines they offer.
Doubt that this could be automated.
The differences are so subtle in these that unless a significant amount was invested in the arbitrage bot, it is very unlikely it'll be picked up. These unique combinations of complementary/supplementary bets can really be picked out by a human.
The fact that OP can consistently find these odds hiding in plain site should be enough proof that arbitrageurs, including botters, simply aren't picking these things up quickly enough to turn a profit. Hence what I said earlier about a *potentially* profitable opportunity.