Your log show "[EC] Engineering changes: A4" that means your customer's HCA revision is A4.
There are A1, A4 revision firmwares.
Also check server vendor's guide and BIOS configuration.
(Intel vt-D, SRIOV, PCIe Payload, etc...)
That server is Intel Xeon MP system maybe have processor module with memory and hot pluging capability.
That module have some chipset and logic.
If there is some firmware co-works with main system board BIOS, BMC firmware that must be check!
Infiniband architecture acts on processor and memory bus behind.
Another log " [ 73.688224] mlx4_core 0000:87:00.0: Failed to initialize event queue table, aborting."
87 means PCI slot number.
Is there 87 PCI slots in that server?
If that true you can try change another above PCI Gen3 x8 slot.
At last you don't describ switch and it's firmware.
What switch is connected that CX-3 HCA?
You must check switch's firmware, too.
Good luck...