After installing the update, running into the problem, reverting back, installing the update, reproducing the problem, reverting back, then installing the update again, the problem has disappeared and my system is now working properly with the Windows update installed.
I originally thought that maybe there was some incompatibility between the relatively new Z390 Taichi motherboard/BIOS and the new update to Windows, but since the problem has completely disappeared, I don't know what could have caused it. Perhaps just a bug in the Windows upgrade process. It was a pretty sizable Windows upgrade that did several automatic reboots as part of its install.
When I originally encountered the problem and saw that I could reproduce it and didn't know how to fix it, I contacted ASRock technical support in case it was an issue with their BIOS or in case it would help to alert them to an issue with their systems. They took awhile to respond, but just suggested I remove all but one stick of memory and remove all overclocking. By then, the problem had already gone away.
(-1 AVX offset) on ASRock Z390 Taichi
with Noctua NH-D15 air cooler
CPU offset voltage of -25mv, runs VRVout 1.240-1.313V on full AVX load, 1.225-1.275V on non-AVX load
2x8GB [email protected] at 1.45V
, G.Skill F4-3733C17Q-32GTZKK (XMP rated [email protected]
EVGA GTX 1060 6GB OC with Corsair RMx 750W power supply
Samsung 970 EVO 500GB NVMe boot SSD and four other drives all in a Fractal Design R6 Case