Events added to S-Planner won't transfer to new phone

[Android Central Question]

I'm trying to move data from my old phone (Galaxy S5 Neo) to my new phone (Galaxy A7). Most of it has happened fine, thanks to Smart Switch. However, very few things have transferred in the S-Planner calendar - a couple of monthly reminders and annual events which are on 'repeat', but other 'repeat' events have not, and none of the very many individual events I record for work. As a self-employed person I need all these records for invoicing, etc.
I tried adding my Google calendar in 'Manage Calendars' and running Smart Switch again, but no joy.