Editing problem

I have a weekly repeating appointment (shopping list).
In the field "Omschrijving" (Description?) I add: "check", and I hit Save.
Works well.
I open the appointment again and add: "check2". Hit Save.
Now this is not being saved. I notice that the app says: "synchronizing", but this takes less time than normal, well working synchronization. Since a few weeks.

Both on Windows and Android