I tested several frequently used recurring scenarios from my customer. Here is
what I found:

- 1 event by week: when added via Front End form, one must edit and validate
twice for the recurrence to be taken into account -> in the db.

- several events by week: last or 2 last events not saved / shown.

- 1 event by month: when added via Front End form, one must edit and validate
twice for the recurrence to be taken into account -> in the db. Another bug:
last event is not present if end date = last event date