I used to bet on corners for Man United games. After getting burned like you I stopped taking the Under corners market on games with ManU playing because too many times at the opening minutes of the match, their attack flies out deep inside the opponent's field without actually scoring any goals, so they're locked into doing corners for the next few minutes. If a goalkeeper saves the ball around this time it usually gets worse because it just rebounds back in play and possibly gets them another corner.
Over corners is also risky because I noticed in some games Man United players have trouble controlling the ball enough to deflect it off someone in the opponent team off the end of the field and so the other team gets free goal kicks instead.
TL;DR Man United's not consistent enough with their corners to be safe at betting on them, it's almost as risky as betting odd/even goals. I'd feel more comfortable betting on Under corners for Liverpool or relegation zone teams (ans possibly even Chelsea these days) than clubs like ManU or Arsenal.
I feel like wagering on lower end of the spectrum games are a bit too risky, I compare them to trading versus leverages. Like in trading, you could just buy bitcoin, wait a month and sell it, usually that will profit you, or you could wait a bit more and still profit, but when you do leverage of 100x, you either end up losing it all, or you end up winning a ton of money. That is the sort of idea, not the same amount of risk obviously and not the same amount of return maybe, but when there is moneyline, and just guess directly who wins, ending up with things like "how many yellow cards" or "corners under over" type of bets become a lot less risky if you ask me.
However this season all teams we thought would be superb ended up not so much superb and favorites do end up losing a pretty decent amount of games as well so it is getting a bit more strange in the regular money lines as well.
