it is a bug, use the following patch (and then execute the ./cache_update.sh):
On 10 Aug 2017, at 14:09, Dario Palmisano
first of all thanks for all the work done by the Caldavzap and Davical
Working with caldavzap v.0.13.1 (on davical v.1.1.5) I noticed that if I
create a new event duplicating a previous one, the previous still appears in
caldavzap interface, but it disappears on other clients like Lightning
(thunderbird add-on) or Apple iCal.
Accessing the davical database entries regarding the two events, it appears
that both have been stored but strangely they have the same UID.
Is it a bug? Does it regard Caldavzap or Davical?
Thanks for your kind cooperation and help