@JasonUK I'm seeing the same thing and have
ticket #246201 open with support. Same conditions, I think. Let us know if there's anything different for you.
Rescue Media Builder for WRBM (boot menu) for the versions that failed with 8.1.7638 previously worked with 8.1.7544, and all show
Windows 10 RE version 2004 (64-bit) while the OS is Windows 10 Pro 22H2 build 19045.3324,
I suspected that Windows Update might have done something to the Recovery Partition for the recent spate of very complicated Security fixes, so I repeated the testing with Secure Boot turned off, but the results were the same ... error code
0xc000A004 and complaints that
\Windows\System 32\ntoskernel.exe was missing or had errors. It's not missing in the Wim in the staging area on the PC, which is where WRBM boots form.
Rebuilding RM with Win PE 10 worked for me, as did resurrecting the ISO file from the previous version of RM with Win RE 10 built under 8.1.7455 and booting it via flash drive.
The system that failed is the second one here to get 8.1.7638; the first was my guinea pig laptop running Reflect v8.1.7638+ on
Windows 11 Home 22H2 22621.2215+ , and it works. It uses
WinRE 11 build 22621 from the Recovery partition.
L.W. (Dan) Danz, Overland Park KS
Reflect v8.1.7638+ on Windows 11 Home 23H2 22631.2715+
Reflect v8.1.7638+ on Windows 10 Pro 22H2 19045.3570+
Reflect v8.1.7638+ on Windows 10 Home 22H2 19045.3570+