BIG problem with wd_check_checksum


I have a huge problem with my website. I use wordfence, and in diagnostics I saw that I have thousands of the same cron job wd_check_checksum running every second.

I don't know what is activating that cron job, I have deleted all the cron jobs in the database in WP_OPTIONS but they keep appearing.

It is a problem because Apache in giving the same error every second

mod_fcgid: stderr: ksum\\";a:1:{s:32:\\"40cd750bba9870f18aada2478b24840a\\";a:2:{s:8:\\"schedule\\";b:0;s:4:\\"args\\";a:0:{}}}}i:1479104808;a:1:{s:17:\\"wd_check_checksum\\";a:1:{s:32:\\"40cd750bba9870f18aada2478b24840a\\";a:2:{s:8:\\"schedule\\";b:0;s:4:\\"args\\";a:0:{}}}}i:1479104811;a:1:{s:17:\\"wd_check_checksum\\";a:1:{s:32:\\"40cd750bba9870f18aada2478b24840a\\";a:2:{s:8:\\"schedule\\";b:0;s:4:\\"args\\";a:0:{}}}}i:1479104814;a:1:{s:17:\\"wd_check_checksum\\";a:1:{s:32:\\"40cd750bba9870f18aada2478b24840a\\";a:2:{s:8:\\"schedule\\";b:0;s:4:\\"args\\";a:0:{}}}}i:1479104819;a:1:{s:17:\\"wd_check_checksum\\";a:1:{s:32:\\"40cd750bba9870f18aada2478b24840a\\";a:2:{s:8:\\"schedule\\";b:0;s:4:\\"args\\";a:0:{}}}}i:1479104821;a:1:{s:17:\\"wd_check_checksum\\";a:1:{s:32:\\"40cd750bba9870f18aada2478b24840a\\";a:2:{s:8:\\"schedule\\";b:0;s:4:\\"args\\";a:0:{}}}}i:1479104824;a:1:{s:17:\\"wd_check_checksum\\";a:1:{s:32:\\"40cd750bba9870f18aada2478b24840a\\";a:2:{s:8:\\"schedule\\";b:0;s:4:\\"args\\";a:0:{}}}}i:1479104828;a:1:......

I have deleted the apache error log file, but after 2 hours the file is already 20GB!

What is happening? Is it a bad plugin? My plugin list:

ADS PRO – Multi-Purpose WordPress Ad Manager - Version 3.2.1 Active
Advanced Access Manager - Version Active
Easy Video Player - Version 1.1.4 Active
Edit Author Slug - Version 1.2.1 Active
Envato Market - Version 1.0.0-RC2 Active
MobiLoud - Version 3.4.5 Inactive
PopUp Pro - Version Active
Real 3D Flipbook - Version 2.30 Active
Reset User Passwords - Version 1.2.2 Active
Restrict Author Posting - Version 2.1.4 Active
Server IP & Memory Usage Display - Version 1.3.3 Active
Share Buttons by E-MAILiT - Version 9.0.2 Active
Snapshot - Version 3.0.3 Active
tagDiv Social Counter - Version 4.1 Active
Theme My Login - Version 6.4.6 Active
Ultimate Branding - Version 1.8.2 Active
Wordfence Security - Version 6.2.5 Active
WP-Mail-SMTP - Version 0.9.5 Active
WPBakery Visual Composer - Version 4.12 Active
WP Defender - Version Active
WPMU DEV Dashboard - Version 4.2 Active
WP Rocket - Version 2.8.23 Active
WP Smush Pro - Version 2.5.2 Active
WP User Avatar - Version 2.0.7 Active

Thank you!