eMClient with CardDAV and CalDAV from purelymail.com

Does anybody use eMClient with with CardDAV and CalDAV from purelymail.com?
WebDAV/CardDAV/CalDAV | Purelymail

CardDAV and CalDAV from purelymail.com are working fine on Android and in Thunderbird.

Use Case:

Create a calendar event in Thunderbird
→ It will be synchronized and displayed in Android. In eMClient the calendar event is not visible.

Create a calendar event in Android
→ It will be synchronized and displayed in Thunderbird. In eMClient the calendar event is not visible.

Create a calendar event in eMClient → It will be synchronized and is visible in Thunderbird and Android. Edit the calendar event in Thunderbird → calendar event is not visible anymore in eMClient.

What can be the reason?