Connect to nextcloud but not sync data

[hubert.kn]

Hi,
I have installed the Davdroid on my moblie (galaxy note 4, android 5). I have added my nextcloud account by two ways:
https://server.pl/nextcloud/remote.php/dav/ In this case there was no CardDav service available in Davdroid, only CalDav was available.
And second one:
https://server.pl/nextcloud/remote.php/dav/addressbooks/users/NAME/contacts/ For this time with CardDav and CalDav services comes up in Davdorid

In each of these two case I could add a new calendar and synchronize it between devices. To be clear, only the name of the a calendar has been synchonized but no content (events) has been copied.

I have tried different CalDav app and it works, so I think there is no problem with the server.

Configuration debug file
Debug 1

Debug file created when I have tried to sync.
Debug 2

Thanks for help

[rfc2822]

Hello,

Your server returns “503 Service Unavailable”, which is a server problem. Please check your server logs.

[hubert.kn]

Hi,
thanks for reply. I have checked server logs. In the moment when I am trying to perform synchronization the following message is occurring.

I have tried multiple times with the same results.

[rfc2822]

@hubert.kn These are the Web server logs. Did you have a look at the Nextcloud logs?

[hubert.kn]

I have turn on debug mode in nextcloud and set log lever for debug. Here you have the result after attempt to synchronization.

[rfc2822]

@hubert.kn Seems like the reason for the 503 is not logged there. However, for me it looks like a server problem. I can’t say anything more detailed without more information. Please contact your server vendor

[hubert.kn]

I have found the next error related with the synchronization. It is logged in server error logs. Could you comment it?

[Wed May 10 13:49:24 2017] [error] [client IP] [host server.pl] (104)Connection reset by peer: ap_content_length_filter: apr_bucket_read() failed
[Wed May 10 13:49:24 2017] [error] [client IP] [host server.pl] (104)Connection reset by peer: Failed to flush CGI output to client

[hubert.kn]

Hi,
I have found the solution. It comes from:
https://help.nextcloud.com/t/davdroid-no-longer-works-with-nc-10-0-1-ovh/3683/4
I have nextcloud 11.0.3

I have applied all hints but helps only:
"
So, in lib/base.php find:
$incompatibleUserAgents = [
// OS X Finder
‘/^WebDAVFS/’,
After add:
‘/^DAVdroid/’,
"

Now I can synchronize events between server and mobile.

But not all works properly.
I have removed in browser the calendar (all) and then I have done synchronization. And the error has occurred (404). The calendar which does not exist on the server can not be remove from mobile.

Debug 1

Debug 2