Fuck ups: 1) Regular dices are heavily weighted on one side. They don’t generate the same entropy as a casino dice. 2) doing it on a hard surface like your table, uneven surface. This reduces the entropy as causes dice to slide. 3) Not shaking properly every time you roll. 4) Most importantly you are relying on coldcard to give you the seed word. How can you trust that device, that’s it’s really really giving you the randomness you generated via dice rolls. For true proper generation you have to do the dice rolls properly plus do the math yourself otherwise it’s always trust involved at certain point.