Moodle calendar is not able to import .ics files with repeated events anymore

Steps to reproduce:

• Login as standard user
• Go to your calendar
• Click "Manage subscriptions"
• Fill the "Import calendar" form
  • Enter an arbitrary calendar name
  • Set "Import from" to "Calendar file"
  • Upload a .ics file with repeated events, e.g. CS6307.000_Introduction_to_Computer_Science_for_Non-Computer_Scientists-2.ics
  • Click "Add"

Expected behaviour / Successful behaviour on Moodle 3.5:

• The file is processed
• A notice is presented:

  Events imported: 1

  Events updated: 0

• All events of the series of repeated events are added to the calendar as expected.

Actual behaviour on Moodle 3.6 / 3.7 / master:

• The file is processed
• A notice is presented:

  Events deleted: 17

  Events imported: 1

  Events skipped: 0

  Events updated: 0

• Only the first event of the series of repeated events is added to the calendar.

As this import has worked before at least on Moodle 3.5, I am marking this bug as regression, but I currently don't know what caused the regression.