In /logs/firmware/patool_extraction/rootfs.img_unblob_extracted/rootfs.img_extract/0-80367616.squashfs_v4_le_extract/usr/share/apache2/previewmode.sh line 3:

. /lib/rcscripts/sh/error.sh

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

In /logs/firmware/patool_extraction/rootfs.img_unblob_extracted/rootfs.img_extract/0-80367616.squashfs_v4_le_extract/usr/share/apache2/previewmode.sh line 35:

  timeleft=$(expr $duration - $uptime)

             ^--^ SC2003 (style): expr is antiquated. Consider rewriting this using $((..)), ${} or [[ ]].

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

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

Did you mean: 

  timeleft=$(expr "$duration" - "$uptime")

In /logs/firmware/patool_extraction/rootfs.img_unblob_extracted/rootfs.img_extract/0-80367616.squashfs_v4_le_extract/usr/share/apache2/previewmode.sh line 36:

  [ $duration -gt $min_duration ] &&

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

                                  ^-- SC2015 (info): Note that A && B || C is not if-then-else. C may run when A is true.

Did you mean: 

  [ "$duration" -gt $min_duration ] &&

In /logs/firmware/patool_extraction/rootfs.img_unblob_extracted/rootfs.img_extract/0-80367616.squashfs_v4_le_extract/usr/share/apache2/previewmode.sh line 37:

  [ $duration -lt $max_duration ] || error "previewmode duration is invalid"

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

Did you mean: 

  [ "$duration" -lt $max_duration ] || error "previewmode duration is invalid"

In /logs/firmware/patool_extraction/rootfs.img_unblob_extracted/rootfs.img_extract/0-80367616.squashfs_v4_le_extract/usr/share/apache2/previewmode.sh line 38:

  if [ $timeleft -gt 10 ]; then

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

Did you mean: 

  if [ "$timeleft" -gt 10 ]; then

In /logs/firmware/patool_extraction/rootfs.img_unblob_extracted/rootfs.img_extract/0-80367616.squashfs_v4_le_extract/usr/share/apache2/previewmode.sh line 39:

    echo "Define PREVIEWMODE 1" >> $RUN_PARAMETERS

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

Did you mean: 

    echo "Define PREVIEWMODE 1" >> "$RUN_PARAMETERS"

For more information:

  https://www.shellcheck.net/wiki/SC1091 -- Not following: /lib/rcscripts/sh/...

  https://www.shellcheck.net/wiki/SC2015 -- Note that A && B || C is not if-t...

  https://www.shellcheck.net/wiki/SC2086 -- Double quote to prevent globbing ...