F4-2666C15D-16GVS on Gigabyte H370 Aorus Gaming 3 wifi

[m3t00]

I have 2x F4-2666C15D-16GVS (4x8G) and can only boot with 2x8 in channel B {DDR_3,DDR_1).
Any stick in channel A {DDR_2,DDR_4) causes boot failure, 5 beeps with DRAM LED light.
https://photos.app.goo.gl/wY36L4oZkxdyB4GWA

I've booted and ran with both sets in channel B so I don't think RAM is bad.
Used G.Skill's configurator to match board before finding Gigabyte's supported list which doesn't list this memory.
http://www.gskill.com/en/configurato...288&model=3337
http://www.gskill.com/en/product/f4-2666c15d-16gvs

I also have a support request in with Gigabyte.
I can't get to BIOS settings withy anything in channel A. v F11 latest flash
Any ideas to make it work in channel A?

[GSKILL TECH]

A2 B2, so it is one slot from each channel not working. Check CPU socket pins to see if they are perfect. Make sure CPU cooler is not too tight or loose.

May be a bad motherboard if nothing helps. When did you purchase it?

[m3t00]

A2 B2, so it is one slot from each channel not working. Check CPU socket pins to see if they are perfect. Make sure CPU cooler is not too tight or loose.

May be a bad motherboard if nothing helps. When did you purchase it?

channel A is slots (DDR4_2 & DDR4_4) both slots in channel A.
channel B is slots (DDR4_1 & DDR4_3)

Cleaned CPU with alcohol and cotton swabs. Gently brushed socket pins with a clean toothbrush. All appeared straight and undamaged. Reassembled.
CPU cooler is Noctura https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
There is no way to overtighten cooler.

Bought board and memory last month. Going to return memory while I still can. newegg 30 days. board has warranty and looks like this will drag on a while.

[GSKILL TECH]

It is one slot from channel A and one slot from Channel B combined that makes dual channel. Slot 1 and 2 away from CPU should be Channel A, slots 3 and 4 Channel B, so A2 B2 slots 2 and 4 should be one set of dual channel, then A1 B1 slots 1 and 3 secondary dual channel.

Get a new set of RAM and motherboard to see if it can work better.

It is more important to replace the motherboard, if possible through the place of purchase since it can be more tricky through manufacturer.