HP Z turbo Dual pro drive dont recognize m.2 in ssd-slot 2 -- HP Z440

[slipperynic]

Hello,
I have a Z440 (broadwell v4, bios v2.26) with a Z turbo Dual pro drive installed (bootable win 7 pro on it) installed as specified in PCIe slot4 (gen3 x8). Up until now i have only had one m.2 disk mounted in the first slot (marked 'SSD1' on the card), but recently purchased three more m.2 disks to fill both slots, as well as another unused Dual pro card i have (now installed in PCIe slot5 (gen3 x16)). For some reason both cards fail to recognize any disk in the second slot (marked 'SSD2' on the card). I have rotated all disks between all slots and possible combinations (except OS drive which exclusively sat in card1 slot1), these are the combinations ive tried:

c1s1 ahci(os)
c1s2 nvme or ahci
c2s1 nvme or ahci or unmounted
c2s2 nvme or ahci or unmounted
=will not boot, says OS is not found

c1s1 ahci(os)
c1s2 unmounted
c2s1 nvme or ahci
c2s2 nvme or ahci or unmounted
=boots c1s1 and recognize c2s1, no other disk recognized

c1s1 ahci(os)
c1s2 unmounted
c2s1 unmounted
c2s2 nvme or ahci
=boots c1s1, no other disk recognized

All disks function if positioned in slot1. All disks get hot to the touch even if mounted in slot2(!), so electrical connection presumably functions properly in both slots on both cards. Since all disks and both Dual pro cards work (albeit not in slot 2) the only software hiccup i can think of would be Windows mistaking the card for a single slot Turbo drive, but that wouldnt explain why OS isnt recognized at all if slot2 is mounted. Since both cards exhibit identical symptoms, im hesitant to believe wonky hardware is at play.

At first i thought it had something to do with mixing AHCI (my OS drive) and NVMe, but i then read in the Quad pro FAQ (cannot find _any_ documentation for Dual pro) that this is not an issue -- only caveat would be that raid is unsupported over mixed protocols.

Other than jumper config, im out of ideas. And since i cant find any documentation (no installation guide, manual, quick spec, white paper or FAQ) for the Dual card, and the jumpers deviate (se attached photo) from the Single or Quad card i just dont know what to do. Ive spend hours duckducking and googling but to no avail, so any help would be greatly appreciated.

Best regards Nicklas.

[slipperynic]

PHOTO: https://drive.google.com/file/d/1NLU_rfAOCcWC4GM8fdbbJQHqKDdGNd-U

[DGroves]

don;t have one of these but as i recall one side says it's for dual sided ssd's and that side is the primary one used if doing raid 1/0 also ONLY ONE SLOT CAN BE USED IF BOOTING FROM THE CARD, the other 3 can be used as a non booting array

Slots 4/5/3 are the only HP recommended slots

so you can not do a bootable raid on this card 

if using 2 ssd's a x8 slot is required, 4 ssd's must use a x16 slot

you must be running a later bios the latest release is highly recommended

you can boot from the card using only one ssd slot as the boot device with the other 3 as non bootable single drives or as a single raid using the 3 remaining ssd'd