Hello beaucoder, I don’t have an answer for your problem, but have you looked at the kernel ring log messages for any clues? You can do this with the following command:
sudo dmesg
You may consider including more detail about your system that may help others troubleshoot your issue.
Regarding 
I would say to always provide the full output from sudo inxi --filter --verbosity 8 as that is usually far more helpful information than people summarize in their requests for help.
I did check the Arch Wiki for anything on “instantaneous wakeup after suspending”, and did find some interesting information, but for other motherboards, so probably doesn’t apply to your situation. Still, you may find this worth researching:
For some Intel Haswell systems with the LynxPoint and LynxPoint-LP chipset, instantaneous wakeups after suspending are reported. They are linked to erroneous BIOS ACPI implementations and how the xhci_hcd module interprets it during boot. As a work-around reported affected systems are added to a denylist (named XHCI_SPURIOUS_WAKEUP) by the kernel case-by-case [3].
Wakeup may happen, for example, if a USB device is plugged during suspending and ACPI wakeup triggers are enabled. A viable workaround for such a system is to disable the relevant wakeup triggers. An example to disable wakeup through USB is described as follows… Power management/Wakeup triggers - ArchWiki