Calendar module not showing Facebook birthdays

[dzsoo]

After a clean install of MagicMirror2 without any errors displayed, i wanted to set up my calendar to show Facebook upcoming birthdays like it was before reinstall, but now i got the following errors and nothing is present in my calendar:
PM2 log

TypeError: Cannot read property 'length' of undefined
    at Object.ical.objectHandlers.END (/home/pi/MagicMirror/modules/default/calendar/vendor/ical.js/node-ical.js:33:22)
    at Object.handleObject (/home/pi/MagicMirror/modules/default/calendar/vendor/ical.js/ical.js:287:41)
    at Object.parseICS (/home/pi/MagicMirror/modules/default/calendar/vendor/ical.js/ical.js:328:20)
    at Request._callback (/home/pi/MagicMirror/modules/default/calendar/vendor/ical.js/node-ical.js:11:24)
    at Request.self.callback (/home/pi/MagicMirror/node_modules/request/request.js:185:22)
    at Request.emit (events.js:182:13)
    at Request. (/home/pi/MagicMirror/node_modules/request/request.js:1157:10)
    at Request.emit (events.js:182:13)
    at Gunzip. (/home/pi/MagicMirror/node_modules/request/request.js:1079:12)
    at Object.onceWrapper (events.js:273:13)

The facebook link for the calendar is ok, i have already checked that. I can display google calendar, facebook events, but facebook birthdays are not functioning.
Does anyone else had this issue, or can help me?

[dzsoo]

After downgrading to Magic Mirror version 2.6.0 Facebook birthdays are working again.

[CarstenD]

Same problem after upgrading to 2.7.1 both calendars do not show any data anymore. Even disabling them does not bring up the default calendar.