I've contacted them once on a customer service issue and a few times with questions and always had great, fast results.
I've seen a few different bowling balls crack from the thumb.(most recently Midnight Vibe) It isn't as common as the fingers, but does happen. I think it has to do with the glue used on the bowling ball. Usually with finger inserts the glue always makes contact with the outer shell of the ball, where as many times the thumb insert being glued in may not.
I went away from finger inserts in 2000-01ish and have never had a ball crack from the fingers since then. I have had one crack from the thumb.(Bonanza/Wrath)
Be good, or be good at it.