No, the invite itself won’t help. We would need the data of the iCalendar feed, including HTTP headers (which may specify the character set).
Can't set sync to 10 or 5 minutes
Setting sync to 10 or 5 doesn’t stick. 15 and greater works fine. Experimentation indicates that the sync interval of 5 or 10 is not silently respected in the refresh rate.
Indeed. Android doesn’t allow that for battery saving reasons.
We had to remove 5 and 10 minutes as options because in recent Android versions 15 minutes is the fastest sync interval which is allowed by the system.