Yea, 10% is 10%, that means 90% chance to miss, 90% is 90% that means 10% chance to miss, just because you miss 15 times and think to yourself but if it's 90/100 then that must be 9/10 times I should get it, then you're thinking of RNG in the wrong way. RNG has the quirk of rolling the lower end at times so it's pretty much bad luck that out of all the zones you had 1 zone where you kept rolling a fail to get the crystal.