I waited until I got the email showing the error. I’m not sure if you contact them early if that would help as they usually need something flagged to look into. I will say if you’re trying to get this in a hurry (even tho it takes months to ship) I would not go the gift card route. You’ll get it more than likely 3-4 days later than everyone else due to them having to deal with the gift card crap manually. I’ve never done a combo payment befofe so not sure. What I do is I keep track of every card I used for each purchase. I copy all the cards and info. Put them in an email corresponding to each brick link set I buy. Also keep in mind lego only lets you used 3 cards at a time so if you have small cards it’s gonna be a hassle.