I think is something wrong with the code. I've stacked 50K coins for 3 days and I got only 4 BSX stacking 3 times which is far away from the 50%, this is something like 1% APR instead of 50%.
yea they've known for a while pos is bugged, I informed them a few weeks ago and I was told the 50% fork would fix it though from the code it was obvious it wouldn't.
they are working on it now apparently, its either a case of stake at the pitiful rewards or hoard weight I'm afraid mate.