I have a question regarding POS:
why a smaller block with weight of 5100 and age of 10.08 stakes first and another one (twice so big) with age of 11.9 and weight of 13500 struggle for 3 days to stake and........nothing?

the coins with 13500 weight have 2.6x more chances of staking than the coins with 5100 weight but luck still plays a factor
id like to think of it this way... you need to get a score of 25000
you roll a 10sided dice and the weight is the multiplier
the smaller block rolls a 5
5 * 5100 weight = 25,500
the bigger block rolls a 1
1 * 13500 weight = 13,500
the smaller block gets a score > 25000 and finds a block
in PoS, the target score is the difficulty
Thanks..