[Evolution] Calendar error: Failed to delete resource

[Kai <kais-lists web de>]

Hello all!

My question is about error messages encountered in the Calendar part of  
evolution:

I frequently get the error

> The calendar backend servicing "[calendar name]" encountered an error.
>
> The reported error was “Failed to delete resource: HTTP error code 412  
> (Precondition failed): Sabre\DAV\Exception\PreconditionFailed
>  An If-Match header was specified and the resource did not exist
>  If-Match[exception][message][header]”.


Can you help me understand this error message?
How do I track down to source of this error and begin to fix it?

I'm concerned that this error suggests that I will have inconsistencies in  
my calendars across my devices.

Best wishes
Kai