Update to calendar invitations cannot be processed: HTTP error code 412

[Jürgen Kübler]

I am using a caldav calendar on a synology NAS and observed issues with calendar invitations I previously received. When I open one of these events I get the warning 'Event cannot be fully edited, because you are not the organizer' which I can live with. However, I cannot process any update I receive to these invitation.
The calendar entry is identified. Message:
  Found the appointment in the calendar “myCal”
When I click on 'Accept' I get the message:
  Unable to send item to calendar “mycal”. Cannot receive calendar objects: Failed to put data: HTTP error code 412 (Precondition Failed): Existing resource matches "If-None-Match" header - not accepted.[if-none-match]
and the event remains unchanged.

Updates are both possible with Thunderbird on the same machine and on my iPhone

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: evolution 3.28.1-2
ProcVersionSignature: Ubuntu 4.15.0-22.24-generic 4.15.17
Uname: Linux 4.15.0-22-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.2
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Thu Jun 14 21:59:26 2018
InstallationDate: Installed on 2018-05-02 (42 days ago)
InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
SourcePackage: evolution
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[shadyyx (krajcar-peter-8)]

So this bug was reported on 14th of June 2018 but it was _confirmed_ only on 7th of November 2018? With this speed we can expect the fix to be rolled out some time end of 2019?

This is a serious issue and I got a plenty of troubles at work already because I always click on "Accept" directly in the email invitation which does not display any error but an "information" saying exactly this: "Unable to send item to calendar 'myCal'. Cannot receive calendar objects: Invalid object" and nothing else.

I have never noticed this small information to popup somewhere in the calendar part of the invitation email and always thought I am fine. Until I got few notices from my boss that I am not accepting the invitations. So I started to look for a problem and only then I realized that all my "accepts" from Evolution are not sent.

Besides that the fact I cannot edit my calendar entries eventhough I am not the organizer is also a problem. I cannot add (invite) anybody else for example and always have to go to Google Calendar (which I have to everytime now to either accept or decline the invitation).

I started using Evolution only recently as I was using Thunderbird for dozens of years before but got tired with it. But now when I see the speed of solving serious issues, I think I am switching back soon.

Evolution v.: 3.28.5-0ubuntu0.18.04.1
OS: Ubuntu 18.04 x64
Desktop: Unity

[Jürgen Kübler (jk-ybn-sw)]

I already switched back to Thunderbird. TB has its issues, too. But I can use it as a productive tool. Unfortunately, evolution is not usable in a professional environment at this stage.

[Jonah (skrap)]

Details here: https://gitlab.gnome.org/GNOME/evolution/issues/413

This is caused by Evolution not having the most up-to-date version of the event. If the calendar is refreshed, the issue may go away.