x86 Attended Sysupgrade 'ext4_allocate_best_fit_partial' fail | 23.05.5 - r24106-10cc5fcd00 > 24.10.0

I realise that x86 with an ext4 expanded setup might not be supported but thought I'd give it a go. Actually seems to have got almost all the way there until ext4_allocate_best_fit_partial.

STDERR:
Package list missing or not up-to-date, generating it.

Building package index...
Downloading http://downloads.openwrt.org/releases/24.10.0/targets/x86/64/packages/Packages.gz
Updated list of available packages in /builder/build_dir/target-x86_64_musl/root-x86/../../../../builder/dl/openwrt_core
Downloading http://downloads.openwrt.org/releases/24.10.0/targets/x86/64/packages/Packages.sig
Signature check passed.
Downloading http://downloads.openwrt.org/releases/24.10.0/packages/x86_64/base/Packages.gz
Updated list of available packages in /builder/build_dir/target-x86_64_musl/root-x86/../../../../builder/dl/openwrt_base
Downloading http://downloads.openwrt.org/releases/24.10.0/packages/x86_64/base/Packages.sig
Signature check passed.
Downloading http://downloads.openwrt.org/releases/24.10.0/targets/x86/64/kmods/6.6.73-1-a21259e4f338051d27a6443a3a7f7f1f/Packages.gz
Updated list of available packages in /builder/build_dir/target-x86_64_musl/root-x86/../../../../builder/dl/openwrt_kmods
Downloading http://downloads.openwrt.org/releases/24.10.0/targets/x86/64/kmods/6.6.73-1-a21259e4f338051d27a6443a3a7f7f1f/Packages.sig
Signature check passed.
Downloading http://downloads.openwrt.org/releases/24.10.0/packages/x86_64/luci/Packages.gz
Updated list of available packages in /builder/build_dir/target-x86_64_musl/root-x86/../../../../builder/dl/openwrt_luci
Downloading http://downloads.openwrt.org/releases/24.10.0/packages/x86_64/luci/Packages.sig
Signature check passed.
Downloading http://downloads.openwrt.org/releases/24.10.0/packages/x86_64/packages/Packages.gz
Updated list of available packages in /builder/build_dir/target-x86_64_musl/root-x86/../../../../builder/dl/openwrt_packages
Downloading http://downloads.openwrt.org/releases/24.10.0/packages/x86_64/packages/Packages.sig
Signature check passed.
Downloading http://downloads.openwrt.org/releases/24.10.0/packages/x86_64/routing/Packages.gz
Updated list of available packages in /builder/build_dir/target-x86_64_musl/root-x86/../../../../builder/dl/openwrt_routing
Downloading http://downloads.openwrt.org/releases/24.10.0/packages/x86_64/routing/Packages.sig
Signature check passed.
Downloading http://downloads.openwrt.org/releases/24.10.0/packages/x86_64/telephony/Packages.gz
Updated list of available packages in /builder/build_dir/target-x86_64_musl/root-x86/../../../../builder/dl/openwrt_telephony
Downloading http://downloads.openwrt.org/releases/24.10.0/packages/x86_64/telephony/Packages.sig
Signature check passed.
Downloading file:packages/Packages
Updated list of available packages in /builder/build_dir/target-x86_64_musl/root-x86/../../../../builder/dl/imagebuilder
Downloading file:packages/Packages.sig
Signature check passed.
Pseudo file "dev" exists in source filesystem "/builder/build_dir/target-x86_64_musl/root-x86/dev".
Ignoring, exclude it (-e/-ef) to override.
error: ext4_allocate_best_fit_partial: failed to allocate 1298 blocks, out of space?
make[3]: *** [/builder/include/image.mk:399: /builder/build_dir/target-x86_64_musl/linux-x86_64/root.ext4] Error 1
make[2]: *** [Makefile:268: build_image] Error 2
make[1]: *** [Makefile:163: _call_image] Error 2
make: *** [Makefile:337: image] Error 2

Start with the image target and the failure at /builder/include/image.mk:399, then trace the Makefile build_image and _call_image targets for the x86_64 root.ext4 output. Reproduce the 23.05.5 to 24.10.0 attended sysupgrade and determine whether the ext4 image can complete without the allocation error.