RANKED BUG???

i play ranked , always put down primary as adc and secondary choice as jungle , guess how many games with adc and how many games with jg ? i play 6 games yesterday and i have JG (second choice) every single times, WTH, you don't get what you get, when there is duo BOT & SUPP they always gets it,and not just one day is being freaking for few weeks now . FIX this ranked system, is BS now, after the patch was released . I feel this is a BUG need to be fix!!!!