after a month none of them was minted.

now in 90days mint probability:

2 of them 263 days age, 99.999% mint probability
2 of them 257 days age, 99.981% mint probability
2 of them 229 days age, 99.978% mint probability

can someone explain the formula or logic how the transaction for POS is selected? Why the highest probability no longer has priority over lower probability. It is pure random or how it work?
And of course I have latest wallet version.