diff --git a/CHANGELOG.md b/CHANGELOG.md
index 75c2af54..1234a898 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,7 +6,7 @@ Version 60 (date TBD)
 
 This is the first release for Ubuntu 22.04.
 
-**Before upgrading**, you must **first upgrade your existing Ubuntu 18.04 box to Mail-in-a-Box v0.51 or later**, if you haven't already done so. That may not be possible after Ubuntu 18.04 reaches its end of life in April 2023, so please compete the upgrade well before then. (If you are not using Nextcloud's contacts or calendar, you can migrate to the latest version of Mail-in-a-Box from any previous version.)
+**Before upgrading**, you must **first upgrade your existing Ubuntu 18.04 box to Mail-in-a-Box v0.51 or later**, if you haven't already done so. That may not be possible after Ubuntu 18.04 reaches its end of life in April 2023, so please complete the upgrade well before then. (If you are not using Nextcloud's contacts or calendar, you can migrate to the latest version of Mail-in-a-Box from any previous version.)
 
 For complete upgrade instructions, see:
 
@@ -15,11 +15,16 @@ LINK TBD
 No features of Mail-in-a-Box have changed in this release, but with the newer version of Ubuntu the following software packages we use are updated:
 
 * dovecot is upgraded to 2.3.16, postfix to 3.6.4, opendmark to 1.4 (which adds ARC-Authentication-Results headers), and spampd to 2.53 (alleviating a mail delivery rate limiting bug).
-* Nextcloud is upgraded to 23.0.0 with PHP updated from 7.2 to 8.0.
+* Nextcloud is upgraded to 23.0.4 with PHP updated from 7.2 to 8.0.
 * certbot is upgraded to 1.21 (via the Ubuntu repository instead of a PPA).
 * fail2ban is upgraded to 0.11.2.
 * nginx is upgraded to 1.18.
 
+Version 57a (June 19, 2022)
+---------------------------
+
+* The Backblaze backups fix posted in Version 57 was incomplete. It's now fixed.
+
 Version 57 (June 12, 2022)
 --------------------------
 
diff --git a/setup/bootstrap.sh b/setup/bootstrap.sh
index 36dc2def..74d6dd20 100644
--- a/setup/bootstrap.sh
+++ b/setup/bootstrap.sh
@@ -31,7 +31,7 @@ if [ -z "$TAG" ]; then
 		echo "Please immediately begin to migrate your data to"
 		echo "a new machine running Ubuntu 22.04. See:"
 		echo "https://mailinabox.email/maintenance.html#upgrade"
-		TAG=v57
+		TAG=v57a
 	elif [ "$UBUNTU_VERSION" == "Ubuntu 14.04 LTS" ]; then
 		# This machine is running Ubuntu 14.04, which is supported by
 		# Mail-in-a-Box versions 1 through v0.30.
diff --git a/setup/nextcloud.sh b/setup/nextcloud.sh
index 8ad27ae7..b0c27052 100755
--- a/setup/nextcloud.sh
+++ b/setup/nextcloud.sh
@@ -29,8 +29,8 @@ echo "Installing Nextcloud (contacts/calendar)..."
 #   we automatically install intermediate versions as needed.
 # * The hash is the SHA1 hash of the ZIP package, which you can find by just running this script and
 #   copying it from the error message when it doesn't match what is below.
-nextcloud_ver=23.0.0
-nextcloud_hash=0d496eb0808c292502479e93cd37fe2daf95786a
+nextcloud_ver=23.0.4
+nextcloud_hash=87afec0bf90b3c66289e6fedd851867bc5a58f01
 
 # Nextcloud apps
 # --------------
@@ -57,10 +57,10 @@ apt_install curl php${PHP_VER} php${PHP_VER}-fpm \
 	php${PHP_VER}-dev php${PHP_VER}-gd php${PHP_VER}-xml php${PHP_VER}-mbstring php${PHP_VER}-zip php${PHP_VER}-apcu \
 	php${PHP_VER}-intl php${PHP_VER}-imagick php${PHP_VER}-gmp php${PHP_VER}-bcmath
 
-# Configure apcu for cli use - required for occ use
-cat > /etc/php/$PHP_VER/cli/conf.d/20-miab.ini <<EOF
-apc.enable_cli=1
-EOF
+# Enable APC before Nextcloud tools are run.
+tools/editconf.py /etc/php/$PHP_VER/mods-available/apcu.ini -c ';' \
+	apc.enabled=1 \
+	apc.enable_cli=1
 
 InstallNextcloud() {
 
@@ -203,14 +203,12 @@ if [ ! -d /usr/local/lib/owncloud/ ] || [[ ! ${CURRENT_NEXTCLOUD_VER} =~ ^$nextc
 		elif [[ ${CURRENT_NEXTCLOUD_VER} =~ ^1[3456789] ]]; then
 			echo "Upgrades from Mail-in-a-Box prior to v60 with Nextcloud 19 or earlier are not supported. Upgrade to the latest Mail-in-a-Box version supported on your machine first. Setup will continue, but skip the Nextcloud migration."
 			return 0
-		fi
-		if [[ ${CURRENT_NEXTCLOUD_VER} =~ ^20 ]]; then
+		elif [[ ${CURRENT_NEXTCLOUD_VER} =~ ^20 ]]; then
 			InstallNextcloud 21.0.7 f5c7079c5b56ce1e301c6a27c0d975d608bb01c9 4.0.7 8ab31d205408e4f12067d8a4daa3595d46b513e3 3.0.4 6fb1e998d307c53245faf1c37a96eb982bbee8ba 1.0.0 3bf2609061d7214e7f0f69dd8883e55c4ec8f50a
 			CURRENT_NEXTCLOUD_VER="21.0.7"
-		fi
-		if [[ ${CURRENT_NEXTCLOUD_VER} =~ ^21 ]]; then
-			InstallNextcloud 22.2.2 489eaf4147ad1b59385847b7d7db293712cced88 4.0.7 8ab31d205408e4f12067d8a4daa3595d46b513e3 3.0.4 6fb1e998d307c53245faf1c37a96eb982bbee8ba 1.0.0 3bf2609061d7214e7f0f69dd8883e55c4ec8f50a
-			CURRENT_NEXTCLOUD_VER="22.2.2"
+		elif [[ ${CURRENT_NEXTCLOUD_VER} =~ ^21 ]]; then
+			InstallNextcloud 22.2.6 9d39741f051a8da42ff7df46ceef2653a1dc70d9 4.1.0 38653b507bd7d953816bbc5e8bea7855867eb1cd 3.2.2 54e9a836adc739be4a2a9301b8d6d2e9d88e02f4 3.0.0 0df781b261f55bbde73d8c92da3f99397000972f
+			CURRENT_NEXTCLOUD_VER="22.2.6"
 		fi
 	fi
 
@@ -241,9 +239,9 @@ if [ ! -f $STORAGE_ROOT/owncloud/owncloud.db ]; then
   'user_backends' => array(
     array(
       'class' => '\OCA\UserExternal\IMAP',
-        'arguments' => array(
-          '127.0.0.1', 143, null
-         ),
+      'arguments' => array(
+        '127.0.0.1', 143, null, null, false, false
+       ),
     ),
   ),
   'memcache.local' => '\OC\Memcache\APCu',
@@ -305,7 +303,7 @@ php$PHP_VER <<EOF > $CONFIG_TEMP && mv $CONFIG_TEMP $STORAGE_ROOT/owncloud/confi
 <?php
 include("$STORAGE_ROOT/owncloud/config.php");
 
-\$CONFIG['config_is_read_only'] = true; # should prevent warnings from occ tool but doesn't
+\$CONFIG['config_is_read_only'] = true;
 
 \$CONFIG['trusted_domains'] = array('$PRIMARY_HOSTNAME');
 
@@ -318,7 +316,14 @@ include("$STORAGE_ROOT/owncloud/config.php");
 
 \$CONFIG['mail_domain'] = '$PRIMARY_HOSTNAME';
 
-\$CONFIG['user_backends'] = array(array('class' => '\OCA\UserExternal\IMAP','arguments' => array('127.0.0.1', 143, null),),);
+\$CONFIG['user_backends'] = array(
+  array(
+    'class' => '\OCA\UserExternal\IMAP',
+    'arguments' => array(
+      '127.0.0.1', 143, null, null, false, false
+    ),
+  ),
+);
 
 echo "<?php\n\\\$CONFIG = ";
 var_export(\$CONFIG);
@@ -367,11 +372,10 @@ tools/editconf.py /etc/php/$PHP_VER/cli/conf.d/10-opcache.ini -c ';' \
 	opcache.save_comments=1 \
 	opcache.revalidate_freq=1
 
-# If apc is explicitly disabled we need to enable it
-if grep -q apc.enabled=0 /etc/php/$PHP_VER/mods-available/apcu.ini; then
-	tools/editconf.py /etc/php/$PHP_VER/mods-available/apcu.ini -c ';' \
-		apc.enabled=1
-fi
+# Migrate users_external data from <0.6.0 to version 3.0.0 (see https://github.com/nextcloud/user_external).
+# This version was probably in use in Mail-in-a-Box v0.41 (February 26, 2019) and earlier.
+# We moved to v0.6.3 in 193763f8.
+sqlite3 $STORAGE_ROOT/owncloud/owncloud.db "UPDATE oc_users_external SET backend='127.0.0.1';"
 
 # Set up a cron job for Nextcloud.
 cat > /etc/cron.d/mailinabox-nextcloud << EOF;
diff --git a/setup/start.sh b/setup/start.sh
index 8ec8475f..509b2fcd 100755
--- a/setup/start.sh
+++ b/setup/start.sh
@@ -70,6 +70,10 @@ fi
 fi
 
 # Create the STORAGE_USER and STORAGE_ROOT directory if they don't already exist.
+#
+# Set the directory and all of its parent directories' permissions to world
+# readable since it holds files owned by different processes.
+#
 # If the STORAGE_ROOT is missing the mailinabox.version file that lists a
 # migration (schema) number for the files stored there, assume this is a fresh
 # installation to that directory and write the file to contain the current
@@ -85,6 +89,8 @@ fi
 if [ ! -d $STORAGE_ROOT ]; then
 	mkdir -p $STORAGE_ROOT
 fi
+f=$STORAGE_ROOT
+while [[ $f != / ]]; do chmod a+rx "$f"; f=$(dirname "$f"); done;
 if [ ! -f $STORAGE_ROOT/mailinabox-ldap.version ]; then
 	echo $(setup/migrate.py --current) > $STORAGE_ROOT/mailinabox-ldap.version
 	chown $STORAGE_USER.$STORAGE_USER $STORAGE_ROOT/mailinabox-ldap.version