currently I am using Rainlendar with three calendards (all rainlendar native ICS on an CIFS/SMB share):
1. Events (this is the one I really use) [cal status : Active, write enabled, no predefined category, monitor changes]
2. Feasts/holidays [cal status: Active, read-only, pre-defined: Holidays, monitor changes]
3. Birthdays [cal status: Active, write-enabled, pre-defined: Birthdays, monitor changes]
I added the third one some days ago. It was created using rainlendar on another PC.
Afterwards all events from the first calendar are getting automatically assigned to the third calendar as well. Even if I remove an event and assign it only to the first calendar it takes rainlendar only about two seconds and the event is again assigned to cal 1 and 3!
The strange thing is that the assignement to cal 1 and three is never written to file. The ICS of cal 1 still contains my regular events and cal 3 the birthdays.