z170 OC Formula Event Viewer Error

I've got an event viewer error occuring on every boot, and it has been occuring since before I installed any graphics card.  The log shows it occured for the first time before I even typed my computer's name during the Windows 7 x64 install. and I don't know whether to ignore it or not.  No crash seems to be associated with it.

Background information.  I am RMA'ing a EVGA 980Ti FTW because it is faulty, crashing in Farcry 4 randomly (event viewer showing a TDR referencing nvlddmkm).  It also failed EVGA OC Scanner X's PhysX 3 Fluid GPU test with the the same file referenced saying the hardware was not installed or the installation was corrupted.  My EVGA 970 FTW performs just fine, though I have not played games extensively with it installed in this system yet.

I've installed, uninstalled, and reinstalled all the latest drivers a couple of times now.  At the behest of Asrock tech support, and against my instincts, I stuck the driver CD in and let it install whatever it wanted.  I then went about reinstalling all the latest drivers manually after that didn't resolve the event viewer error.  I've run passmark's Memtest 86 in UEFI mode and passed all tests.  I've run Folding at Home for hours and hours and the system is stable, with only a couple "true" early_unit_end's occuring for the same project number 10xxx on the CPU slot with the core status 72 (114). After investigating that, they could just be normal since there were no machine instability messages.  Prime 95 is stable, but I haven't run a marathon of tests with it yet.  Temps are good.  That concludes the backstory. :)

CPU: Intel Core i7-6700K 8M  ($420 - Custom)

Motherboard: ASRock Z170 OC Formula  ($238 - Custom)

Memory: CORSAIR 16GB (2 x 8GB) Vengeance LPX  ($125 - Custom)

Video Card: EVGA GeForce GTX 980 Ti 06G-P4-4996-KR  ($640 - Custom)

Power Supply: EVGA 850W 220-G2-0850-XR  ($110 - Custom)

Storage: WD 1TB BLACK SERIES WD1003FZEX  ($75 - Custom)

Storage #2: SAMSUNG 500GB 850 EVO MZ-75E500B/AM  ($155 - Custom)

Case: NZXT Phantom 820 Series CA-PH820-G1 820  ($235 - Custom)

CPU Cooler: Noctua NH-D15  ($90 - Custom)

Optical Drive: ASUS DRW-24B1ST/BLK/B/AS  ($20.38 - Custom)

Total: $2,108.38

TLDR: This event viewer error occurs every time the system boots:

Event 56, Application Popup

Driver ACPI returned invalid ID for a child device (5).

No crashes seem to be associated with this error. Ignore or keep investigating?

If it is driver related then performing a fresh install as you say you did should have corrected it, another option is to use DDU and uninstall from safe mode and try a few different driver versions and see if that clears the issue.

The error also occurs fairly frequently on factory overclocked GPUs that for one reason or another are not stable at their factory overclock. Loading MSI afterburner and dropping the clocks to stock or lower will clear the issue in a case like this. RMA the GPU if this works.

Another GPU fault is inadequate power getting to the GPU. There are 2 things you can try here:

1. Set "Power management mode" in Nvidia control panel to "prefer best performance" instead of "adaptive". This has corrected the issue for many users.

2. If that still does not work then use MSI Afterburner and set "Power limit" to about 70% and test for TDRs. If this works then the issue is due to a power problem, either in the GPUs power system or the power going to the GPU is unstable or inadequate. Inadequate/unstable power could be caused either by an unstable PSU/poor connection or, an issue with the motherboard not providing enough power to the PCIe slot. Be sure you have both the 8 and 4 pin connectors on your motherboard connected and that they are properly seated. 

If after all this you still have the issue then sending back the board is the only remaining option.