Looks like it's a problem with the script when it attempts to parse the kernel version.
Line 29 in the plugin_update_helper script attempts to extract the kernel version :
NEW_KERNEL_V="$(grep -E -A2 "Linux kernel" /boot/changes.txt | grep -E "Unraid" | awk '{print $3}' | sort -V | tail -1)"
but with this release, it returns (CVE-2021-33909. Replacing $3 bt $2 in the awk command return the proper version 5.15.40-Unraid.