Is it gamble even though it have the same speed and is from the same company?
yes I have had 2 sticks the same make. model and made 1 apart, the serial numbers were in sequence and they would not work together.
impurities in the chips. where the chips are cut from the die, and many other variables can effect their ability to work together (as one unit). this is why kits are tested, verified, and guaranteed to work together.