There are 42 CLL algs, which means its a roughly 1 in 42 chance to get this case (i say roughly because some cases appear more often than others but i cant find out how often this specific case appears). There are 4 different possible aufs so that makes it 1/42 x 4 which is 1 in 168 solves. But then getting this same exact case 2 additional times in a row makes it 1/168^3 which comes out as 1 in 4,741,632 solves which makes your estimate of 1 in 5 million likely very accurate. Incomprehensible luck.
