Zero byte zip file

I’ve been using the backup feature for a few years with no problems. Each day a new zip file is created with the database backup. Since August 17th each day it is producing a zero-byte zip file and the .sql file is also in the folder. I assume when using the zip option, the plugin first creates a .sql file, then compresses it producing a zip file, followed by deleting the .sql file. There is nothing recorded in the log except that the file was created. Details from the log entry are below.

id => 115039
module => backup
type => notice
code => file-stored
timestamp => 2018-08-25 21:49:25
init_timestamp => 2018-08-25 21:49:16
remote_ip => 184.57.65.40
user_id => 1
url => https://www.(removed).org/wp-admin/admin-ajax.php
memory_current => 31289872
memory_peak => 75059408
data => Array
settings => Array
all_sites => [boolean] false
method => [integer] 2
location => /var/www/vhosts/www.(removed).org/wordpress-backups
retain => [integer] 60
zip => [boolean] true
exclude => Array
0 => itsec_lockouts
1 => itsec_log
2 => itsec_temp
enabled => [boolean] true
interval => [integer] 1
last_run => [integer] 1535148536
mail_success => [boolean] true
file => /var/www/vhosts/www.(removed).org/wordpress-backups/backup-(removed)-20180825-174916-YNje4Hw000cfYDWiIjCDdEknhX6m5c.sql