Trouble with RAM configuration

I have an Asrock x99 Extreme6 motherboard with 2x8GB memory modules. These were bought in a pair and have the exact same stats. I used to have them in dual channel mode with them plugged into A1 and A2. I was not the one who configured this. However, I recently learned that any module plugged into A1 would cause the computer to crash on almost random occasions. More than likely a problem with the board. However, the manual both online and in my hands says I should be putting the memory modules into A1, B1, C1 and D1 to get dual memory mode. I've tried every combonation I can think of without plugging memory into A1 and none seem to get me my required status of 'dual memory' mode on CPU-Z. Can someone explain to me how I might be able to get my machine back into dual memory mode without using A1?

Now that you used the screenshot I realized my computer was using dual channel memory mode. It was just not reporting it to CPU-Z. This is fine. Thank you for the response.