Course Schedule doesn't work anymore after update from 13.13 to 13.18

Hello!
Course Schedule doesn’t work anymore after update from 13.13 to 13.18.
I have the error:

Failed to get method for command frappe.desk.form.utils.validate_link with module 'frappe.desk.form.utils' has no attribute 'validate_link'

And nothing. No any schedule.
What should I do for restore this?