One thing that I'm always afraid of is retained sperm from a previous breeding.
I bred my mojave to my pin and lesser last year. They locked all the time for months. She never ovulated. I was thinking about breeding my clown to her this year, but I'm really hesitant to do so because I worry about retained sperm.
There are cases where a clutch is sired by both the current breeding males and males used in the previous season. I'm just worried about something like that happening to me in regards to hets. lol.
As for genetic guarantees, usually sellers give ~3 seasons to prove out that animal. And the buyer gets either a refund, partial refund, or discount on next purchase if the animal doesn't prove out and they want to pursue some sort of action. I don't think many people offer a visual animal as compensation. It's probably just easier to refund the buyer.