ASUS ROG Strix Z790-E Gaming wifi Q-code 77 with red light when PC set to sleep

[206inthe919]

Newly-built PC (2 weeks tomorrow). Getting recurring system resume/boot failure with Q-code 77 in red on motherboard when putting PC to sleep.  Requires hard power cycle on PC case, power cycle on PSU, then restart.

No change in behavior after doing all of the following:

Updated BIOS to 1503
Clear CMOS
Reduced RAM to one stick
Reseated GPU
Checked all motherboard connections (FPANEL, USB, SATA, etc.)
Changed from DisplayPort cable to HDMI 

Aside from checking motherboard standoffs for the faint potential of a short, I'm completely stumped. The system is otherwise solid, runs games perfectly, stays cool (with the occasional iCue vs Armoury Crate weirdness)... but this sleep issue and resulting Q-code is eluding me.

System specs:

ASUS ROG Strix Z790-E Gaming Wifi II
Intel Core i7 13700KF (no bent pins, stock, no overclock)
ASUS ROG Strix 4070 Ti Super OC (seated in top 16x slot)
Corsair RM1000x Shift ATX PSU
Corsair iCue Link H150i AIO
Corsair Vengeance RGB DDR5 32GB (16GB x 2)
Samsung 990 Pro M.2 Gen 4 (seated in middle PCI slot)

Open to any/all suggestions or guidance, thanks.

[Jiaszzz_ROG]

Hello @206inthe919 

We apologize for the delayed response due to local holidays.
Thank you for reaching out to us and for sharing detailed information about the situation and the troubleshooting steps you’ve already tried.
Based on your description, the issue does not occur during a cold boot but rather after waking from sleep.
In addition to verifying and reconnecting the three power connectors (A, B, and C) and, if possible, cross-testing power cables or the PSU.

We also recommend trying the following settings to see if there’s any improvement:
- In the BIOS, try setting DMI Link ASPM Control and ERP Ready to [Disabled].
- In Windows, disable Fast Startup and check if Link State Power Management under PCI Express in Advanced Power Settings is set to off, and further verify if there are any potential restrictions in the power plan.
If needed, try booting with a minimal setup, removing as many external devices as possible, and observe the behavior after waking from sleep.

Thank you.