on V8.5.0, I have this error on log files, and CRON always stopped...
2020-06-19 11:54:08.914 ===== TRACE ===== ERROR - Cron::checkEmails() - IMAP extension not enabled in your PHP config. Cannot connect to IMAP Mailbox.
I do not have this pb on V8.4.x
Possibly you tried the new feature "import tickets from emails"
Configuring the first mailbox activiates the Cron Imap check.
Disable the feature in Global Parameters : set "email input check cron delay (in seconds) " to -1
NB : issue tells you you try to use IMAP feature but don't have php-imap installed