Edit your Nextcloud client config (~/.config/Nextcloud/nextcloud.cfg) and add these lines under [General]:

timeout=1200
maxChunkSize=100000000

Use this command to change your LDAP host in case you need to switch to a backup server:

sudo -u www-data php /var/www/nextcloud/occ ldap:set-config ‘s01’ ldapHost 10.0.2.3