[Evolution] Problem in write support CalDAV 3.16

[Matthijs van Wolferen <matthijsvanwolferen fastmail fm>]

Just upgraded to Fedora 22 with 3.16.1 installed.
Still have this strange problem where I can't write to my CalDAV
calendar, hosted by Fastmail.
Thunderbird w. Lightning on same install gives no such problems.
Strange thing is, I don't get an error on console. 
No problem with read/write on other clients either (win7 + tb, win7 +
rainlendar, bb10 smartphone). 
How can I troubleshoot this issue?