When more than one scheduled task is specified in Websites & Domains --> Scheduled Tasks (1)one of the tasks receives incorrect
SHELL directory is assigned to a task.
This is Plesk internal issue with id #PPPM-3819 , which is planned to be fixed in future product updates.
Perform either of the following to fix the issue:
SHELLfor a certain task. It should be set as shown below:
# vi /var/spool/cron/customer
/bin/shoption in Web Hosting Access settings in Hosting panel
Note: This workaround can potentially decrease server's security.