I do not use any cloud services personally but I use an Exchange account for work and I can definitely confirm that particularly the calendar sync, but also deleted emails, are all over the place. The very first thing my Jolla did when I first signed up to the Exchange account was it duplicated the Easter Monday calendar entry to every single day of the year for many years into the future. More recently, a rescheduled calendar entry was not rescheduled in my phone, I had to do that manually.