Odd Random error with Random int

Okay so i have this rpg i’m making in which i have all the stats for each of the 12 playable characters saved as struts. these struts are in an array. On level up, it’s suppose to check the array for the leveled up character, take those stats, add stats from a range or 0 to their max possible stat up (different for each character) then put that back into the strut. this works fine (i think) it takes the stats and adds a random number then spits back out an increased number. the problem is that, when used in repetition, the new starting int is different from the last int. I have no clue as to why it starts again at random. the odder part about all this is that for the first 5 or so, IT WORKS. then it just decides to start fumbling around.