In /logs/firmware/unblob_extracted/firmware_extract/1568982-13971496.squashfs_v4_le_extract/etc/uci-defaults/09_fix-checksum line 6:

. /lib/functions.sh

  ^---------------^ SC1091 (info): Not following: /lib/functions.sh was not specified as input (see shellcheck -x).

In /logs/firmware/unblob_extracted/firmware_extract/1568982-13971496.squashfs_v4_le_extract/etc/uci-defaults/09_fix-checksum line 9:

	local kernel_size=$(sed -n 's/mtd[0-9]*: \([0-9a-f]*\).*"kernel".*/\1/p' /proc/mtd)

        ^---------------^ SC3043 (warning): In POSIX sh, 'local' is undefined.

              ^---------^ SC2155 (warning): Declare and assign separately to avoid masking return values.

                          ^-- SC2046 (warning): Quote this to prevent word splitting.

In /logs/firmware/unblob_extracted/firmware_extract/1568982-13971496.squashfs_v4_le_extract/etc/uci-defaults/09_fix-checksum line 11:

	[ "$kernel_size" ] && mtd -c 0x$kernel_size fix$1 firmware

                                       ^----------^ SC2086 (info): Double quote to prevent globbing and word splitting.

                                                       ^-- SC2086 (info): Double quote to prevent globbing and word splitting.

Did you mean: 

	[ "$kernel_size" ] && mtd -c 0x"$kernel_size" fix"$1" firmware

For more information:

  https://www.shellcheck.net/wiki/SC2046 -- Quote this to prevent word splitt...

  https://www.shellcheck.net/wiki/SC2155 -- Declare and assign separately to ...

  https://www.shellcheck.net/wiki/SC3043 -- In POSIX sh, 'local' is undefined.