During installing of kernel 5.5.5 i see
==> Generating module dependencies
==> Creating gzip-compressed initcpio image: /boot/initramfs-linux-fallback.img
==> WARNING: errors were encountered during the build. The image may not be complete.
That is not the ISO, that is new kmod, patch needed for mkinitcpio (tested here fixes the issue). ISO does not have kmod 27, since it breaks the ISO creation now.