I have been using this Quad HDMI Recorder card on our original PC setup for few years and we didnt have problem with delay at all until recently we got some profit and we bought new PC which is more powerful and wanna make it into main broadcast PC so we take the card from OLD PC to plug in NEW PC. When it all work fine and received feed as normal until we start adding more than 1 Source in Vmix from the same card it give us at least 2sc delay from the feed. Here our Example:

*OLD PC:
-Slot 1 : PC HDMI
-Slot 2 : PC HDMI
-Slot 3 : Camera HDMI
-Slot 4 : PC HDMI

Spec :
RAM : 32GB
GPU : RTX 3060
CPU : Core i7-11700K
MOBO : TUF GAMING Z590-PLUS WIFI

*New PC:
-Slot 1 : PC HDMI
-Slot 2 : PC HDMI
Just this 2 already give the delay.

Spec:
RAM : 32GB
GPU : RTX 3080
CPU : Core i7-12700KF
MOBO : B660 GAMING X DDR 4

I wanna mention that all the cable and PC are all the same we been using it for years just this new PC that start giving problem.

On your old PC, the Decklink Quad HDMI (x8) was plugged into a PCIe x4 slot.
This wasn't optimal because this slot is managed by the Z590 chipset and not by the i7-11700k CPU.

However, it still worked because you only needed to use 4 inputs at 1080p, since one 1080p input requires x1.

For an optimal configuration, you would have needed a motherboard where the 20 PCIe lanes of the i7-11700k are distributed as follows:

PCIe slot 1 = x8
PCIe slot = x8
M.2_1 port = x4

like Asus ROG Strix Z590-E Gaming

or, if you only use the Decklink card at 1080p

PCIe slot 1 = x8
PCIe slot = x4
M.2_1 port = x4
M.2_2 port = x4

like Asus ROG Strix Z590-F Gaming

On the new PC, it's the same story.
The PCIe slot to which the Decklink Quad HDMI is connected is also connected to the B660 chipset, and not to the i7-12700KF CPU.

Except that this slot is x1.
So you can only get one 1080p input.

For an optimal configuration, you need to change the motherboard and RAM.
For a Z690 / DDR5 motherboard that distributes the PCIe CPU lanes across its slots in x8/x8/x4.

For example:
MSI MPG Z690 Carbon
Asus ProArt Z690 Creator
AsRock Z690 Taichi