S Planner not syncing with multiple calendars

Hi

I have an Galaxy S5 neo, android version 5.1.1

I sync my calendar with outlook.com and my work's exchange account.

If I create an event/apportionment in outlook (exchange) I can see it in my S planner. The same when I create appointment in outlook.com.

But when I create the event/appoinment in S planner, it is just syncing with the default (or whatever calendar I choose). Not will all of them. Currently all my calendar are set to sync under the option "Manage my calendars".

I want to be able to push the appointment/event that I create in S planner to all my calendars. The same happens with android google calendar.

Any idea how to fix this?

Thanks.